Monthly Archives: July 2009

colormunki colour management

Colour management is needed to try to ensure that when using computer systems colour fidelity is achieved across different machines and between soft and hard copy. Computers represent colour as three numbers, RGB. But the same RGB values displayed on different monitors will usually result in a different on-screen colour. In addition, there could be colour gamut issues; one monitor may be able to display colours that are simply out of the achievable range of another. When we consider printers the problem is even worse. The gamut of a printer is very different to that of a computer display. And printers tend to represent colour in terms of CMY or CMYK values. So the colour-management software has rather a lot to do to satisfy users.

A great deal of colour management goes on in computer systems of which the average user is completely unaware. This uses default settings and makes various assumptions but is normally good enough so that reds appear red and blues appear blue on any computer display or printer. Colour management has been built in to Apple software for a long while and is now also part of the Microsoft operating system. But the professional user may require more than is offered by the basic colour management that comes as part of all new systems. However, professional-level colour management comes at a cost and it’s not just financial. It is usually necessary to have to characterize each device (monitor display, printer etc.) that is to be used; and this requires colour measurment and some knowledge of colorimetry.

I recently came across a new product – ColorMunki 1.1 – released by X-rite that promises enhanced colour performance for colour-critical users. This seems to be an interesting product in that it is aimed at designers and photographers.

ColorMunk 1.1 – – is in fact a suite of software that also include a device for measuring colour. I am looking forward to trying this out. If anyone has any experience of this system that they would like to share it would be vey helpful.

sheep change colour

A few weeks ago I wrote about the moths in the UK that are now changing colour as a result of changes in their environment. The species that darkened in colour in response to the industrial revolution is now becoming lighter again –

Today I came across a story about sheep changing colour; this time in response to global warming, apparently. According to Dr Maloney at the University of Western Australia,  in colder environments, mammals with darker coats absorb more solar radiation and so need to expend less food energy keeping warm than do their lighter counterparts. He has found fewer dark coloured Soay sheet over the last 20 years and links this to changing temperatures. H expects the proportion of dark sheep to decrease further over the coming years. His work was reported in the Royal Society journal Biology Letters but a summary is availale online at The Telegraph –—climate-change-making-sheep-change-colour.html.


Colour personality test

There has long been an interest in trying to predict aspects of personality based on colour preferences. The Lüscher test is perhaps the best known example. There are a number of on-line tests that purport to be based on Max Lüscher’s system, for example, In this test you are asked to select eight coloured patches in order of preference. These are the patches:


So I just did the test on-line and these were some of the things the test said about me:

“Craves change and new things, always looking for new adventures and activities. Becomes restless and frustrated when he has to wait to long for things to develop. His impatience leads to irritability and a desire to move on to the next project.”

“Highly optimistic and outgoing personality. Loves to learn new and exciting things, and craves new interests. Looking for a well-rounded life full of success and new experiences. Does not allow himself to be overcome with negative thoughts or self-doubt. Takes life head on, with enthusiasm. “

Well, it’s interesting, because it does sound a little bit like me to be honest. Does anyone who knows me agree? But then, we should be aware of  the Forer effect (also called personal validation fallacy): the observation that individuals will give high accuracy ratings to descriptions of their personality that supposedly are tailored specifically for them, but are in fact vague and general enough to apply to a wide range of people. We all tend to do this with horoscopes in the daily newspapers. So, I tried the test again – this time using a random colour selection – and these were the corresponding statements:

“Is a little on the lazy side when it comes to putting forth a lot of effort. Needs to build roots and have a peaceful, loving partner.”

Relies on love and friendship to bring him happiness. He is in constant need for approval and this makes him willing to help others in exchange for love and understanding. He is open to new ideas as long as they are productive and interesting.

These certainly don’t sound so much like me. Perhaps there is something in it. Of course, we would need to do a proper scientific study to really get to the bottom of what is going on. Which brings me to the purpose of this post – today I came across a colour personality test that does seem to have had some statistical/scientific validation. The test is called the Dewey Color System ( This test has been assessed with a scientific study conducted by Rense Lange and Jason Rentfrow, the latter being a Lecturer in Psychology at the University of Cambridge (UK). The work has not yet been published but a “pre-journal white paper report” can be downloaded – I will leave it to you to read the report and make your own conclusions.

Indigo – a colour of the rainbow?

From time to time I come across web pages and groups of people who get irrate about indigo being in the rainbow. There is even a facebook group called “Get Indigo out of the rainbow”. It was Newton who suggested that the rainbow contains seven colours: red, orange, yellow, green, blue, indigo and violet. It has been suggested that, at the time, Newton was trying make some anology with the musical scale and the octave (with its seven intervals) and hence was keen to identify seven colours in the rainbow or visible spectrum. Many modern commentators claim that only six distinct colours can be observed in the rainbow.

Interestingly, the facebook group referred to above would like to eject indigo from the spectrum on the basis that it is not a primary or secondary colour but rather a tertiary colour. The group shows the following colour wheel:

colour wheel

In this so-called painters’ wheel the primary colours are red, yellow and blue and the secondary colours are orange, green and violet. It is argued that since six of the colours in the rainbow are primary or secondary colours in the colour wheel and indigo is not, then indigo has no right to be there. This is wrong on so many levels it is hard to know where to start.

The first thing I would have to say is that this argument seems to ignore the difference between additive and subtractive mixing. Additive mixing – – describes how light is mixed and the additive primaries are red, green and blue. The additive secondaries are cyan, magenta and yellow. Orange is not in sight – and yet surely if we are to make an argument for inclusion in the spectrum based on primaries (and/or secondaries) then it is the additive system that we should be using since the spectrum is emitted light.  

The optimal subtractive system primaries are cyan, magenta and yellow (with the secondaries being red, green and blue) though the artists’ colour wheel (which is like the painters’ wheel above) has red, blue and yellow as the primaries. 

In my opinion there is nothing special about the colours that we see in the spectrum. Indeed, orange is clearly a mixture of red and yellow and does not seem to me to be a particularly pure colour. I just do not think that arguments to exclude indigo from the spectrum based upon colour wheels or primary colours is valid. That said, I have already mentioned that many people believe that indigo cannot be seen in the spectrum as a separate colour; but this is a phenomenological observation not dogma. I am one of those who believe that indigo and violet cannot be distinguished in the spectrum and therefore I agree with the aims of the facebook group even if I do not agree with their arguments.

The really interesting question is why we see six (or even seven) distinct colour bands in the spectrum when the wavelengths of the spectrum vary smoothly and continuously? I have postulated some possible reasons for this in an earlier post – – but it is far from a complete and convincing explanation. It may explain why we see distinct colours in the rainbow, but why six and why those six in particular. Comments on this would be very very welcome.

Colour names affect consumer buying

Have you ever wondered why, when you look at a rainbow, you see distinct bands of colour? You may see red, orange, yellow, green, blue, indigo and violet (though more likely you will not be able to distinguish between indigo and violet). We know that the wavelength of light in the visible spectrum – – varies smoothly and continuously, so why don’t we see a smooth and continuous colour spectrum? Why do we see distinct colour bands?


In my opinion the reason we see bands is because of something called categorical perception. We tend to want to group things that we perceive together into one class or another. But this grouping is not just a matter of putting things into boxes; it has an impact on how we perceive those things. We see categorical perception everywhere – indeed, I have often wondered whether even the periodic table of chemical elements is a true and accurate representation of how the world is or whether it stems from our categorical perception.

A recent study by Skorinko at the University of Virginia and colleagues at Rice University (published in Psychology and Marketing, 2006) finds that consumers have a more positive reaction to products whose colours are given rather exotic and flashy names such as mocha compared with the same products that are given plainer and genric names such as brown.


 And how is that linked to the early statements I hear you ask (even though you asked very quietly)? Well, the authors hypothesise that the reason for the improved consumer reaction to the fancy colours is …. categorical percetption. The fancy names stimulate a more positive category than their plainer alternatives. It is also suggested that more ambiguous descriptions (mocha as opposed to brown, for example) yield higher consumer acceptance and safisfaction. I cannot resist finishing this blog with the last line from the paper by Skorinko et al. (2006) who write:

Indeed, the judgement of “that we call a rose” seems to be influenced by its name (Shakespeare, 1595). 

CIE system of colorimetry

For about 100 years there has been an international system for colour specification – it’s called the CIE system. The acronym comes from Commission Internationale de L’Eclairage.

This system is based on the notion of additive colour mixing –

Since it is possible to mix together three primary lights and make a wide gamut of colours (though not, of course, all colours) the principle is that the amounts of these primaries that an observer would use to mix togther to match a colour is a useful specification of that colour. We refer to these amounts as tristimulus values. One could imagine a visual colorimeter whereby an observer would try to match a colour that is to be specified by adjusting the intensities of three primary lights that are mixed together – once a match is obtained then the tristimulus values would define or specify the colour. All that would be necessary would be to able to decide on a set of primaries and manufacture the visual colorimeters so that they are very consistent from one device to the next. It would be a little clumsy though to have to use one of these visual colorimeters. But in principle it could work.

Fortunately the CIE does not require the use of such visual colorimeters since in 1931 the CIE measured the trismumulus values that observers made when matching various colours. These were averaged to create the so-called CIE standard observer.  And here’s the really clever bit. Having defined the CIE standard observer it is possible to calculate the tristimulus values (the amounts of the three primaries that an observer would use to match a colour) without any further observations. All that is required is that we know the amount of light at each wavelength reflected by a sample or (in some cases) emitted from a device such as computer display and then – by using our knowledge of the CIE standard observer – it is possible to calculate the tristimulus values.

So what were the primaries. If you have read my previous post, What is a colour primary – – you’ll know that the choice of colour primaries is somewhat arbitrary. Well, in fact the original determination of the standard observer what carried out in England using red, green and blue primaries. But the data obtained were later modified to refer to a different set of primaries known as X, Y and Z. It was necessary to make this adjustment because using any set of real primaries it was impossible to match any colour with mixtures of the primaries; using RGB meant many colours could be matched, but not all. So a set of so-called imaginary primaries was conceived which could – in theory – be used to match all colours. So the tristimulus values of the CIE system are known as X, Y and Z. 

In fact, it didn’t really matter which set of primaries was used; the CIE system was concerned with colour matching. If two samples have the same tristimulus values then they would be a visual colour match no matter which set of primaries was used. So the choice of primaries really was not critical.

Today many instruments are commercially available – colorimeters, reflectance spectrophotometers, radiometers) – that, with the use of software, allow the CIE XYZ values to be measured; these instruments are extremely valuable in many industrial and commercial applications. The CIE system is still very much alive today, though many users often prefer to use one of the more advanced colour spaces – such as the CIELAB colour space – which was defined by the CIE in 1976 and whose values are very easily calculated from the CIE XYZ values.  For further information about the CIE please visit their web site –

colour and brand loyalty

I’m on the way to a dental conference in Houston to speak about tooth whitening. So with a few hours to kill in Philadelphia airport I am taking the time to read Martin Lindstrom’s Buyology –


He describes an experiment that he conducted where he invited 600 women into a room and presented each of them with a blue Tiffany’s box. Their heart rates were being measured and they went up by 20% when they received the box. The interesting thing is, the women never even saw the logo. Just seeing the colour – and the presumed association of that blue colour with the Tiffany brand – was sufficient to excite them. Indeed, the book describes a study by Seoul International Color Expo that showed that colour increases brand recognition by upto 80%. Interesting ….

Orange wedding

Tomorrow I’m flying to Houston to present at a meeting of the Society of Color and Appearance in Dentistry; So it was a strange coincidence that I came across a news story today that there is a trend in Houston (of all places) for people getting married – possibly brides, though I wouldn’t be so sexist as to suggest that – to use orange as a key colour in their wedding decorations. Interesting to see that orange is still a fashionable and contemporary colour. I knew I was right using orange as a main theme for the appearance of this blog! For the full story visit