Welcome to my blog

I am passionate about sharing my knowledge about colour to anyone who is prepared to listen. I work as a professor of colour science at the University of Leeds, in the School of Design, but I have held academic posts in departments of Chemistry, Physics, Neuroscience, and Engineering. Sounds like a mixed bag, but my interest was colour chemistry, colour physics, colour neuroscience, colour engineering and colour design. You see I have come to believe that colour is the perfect meta-discipline and that to understand colour you need to be able to understand (but not necessarily be an expert in) different fields of knowledge.

One way to use this blog is to just browse through it and dip in here or there. However, another way is to click on one of the categories (that interest you) such as culture, design, fun, and technology and see posts in that area. You can find the categories on the right-hand side of the page if you scroll down.

You can also comment on the blogs. I really like this, even if you disagree with me. Someone once said to me if you put ten colour physicists in a room and ask them a question (presumably about colour physics) you’ll get 10 different answers. Well, I guess not all of you reading this are colour physicists. Given our different interests and backgrounds, and given the complexity of colour, it’s not surprising that we will disagree from time to time. And that is rather the fun part.

If you have a technical question you’d love me to answer you can click on Ask Me and post it there. You can also email me at s.westland@leeds.ac.uk

The Wizard of Oz

This week I had to mark about 50 essays that had been submitted for the Colour: Art and Science module I teach at the University of Leeds. One essay looks rather like another after the first 10 or so. So it was a delight to discover that one student had decided to focus on a movie – The Wizard of Oz – and demonstrate her understanding of colour by analysing this classic movie.

It reminded me of a story my mother told me. When she went to see the Wizard of Oz in the cinema (she would have been about 8 at the time) she had never seen a colour movie before. She was so much looking forward to this new-fangled and exciting technology. It’s hard to imagine how exciting that would have been – if every movie you had ever seen had been in black and white!!

Well, imagine her disappointment when the movie started and the movie was black and white after all. For those who don’t know, the movie starts off in black and white (in the Kansas scenes) and only turns coloured when Dorothy is whisked off by the tornado and dropped off in the land of Oz. It must have been a wonderful moment when the screen just turned full colour!!

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 – http://colourware.wordpress.com/2009/07/13/additive-colour-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 – http://colourware.wordpress.com/2009/07/20/colour-names-affect-consumer-buying/ – 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.

AIC2017

There is still time to submit an abstract for AIC2017 which will be held this autumn in Jeju island in South Korea. It’s probably the largest colour conference of the year and every four years they have an especially large one called the congress. We hosted the last congress in UK but this time it is the turn of South Korea. If you can attend this conference I highly recommend it as a way to meet all sorts of interesting and colourful people.

colour lighting



Very excited with the temporary installation of our new spectral lighting system at Leeds University. Whereas most coloured lights are based on RGB, we have a system that has a lot of spectral control (it works by having 11 different coloured LED primaries). We have several PhD students who are using these lights with their research. Nic and Yiting are looking at the effect of light and colour on alertness and also on impulsivity. Meanwhile, Soojin (pictured) is looking at the effect of colour on creativity (though in her study we won’t be using really saturated colours like those shown in the pictures). Hoping for some great publications on this soon. However, if you are interested in whether coloured lighting can affect heart rate and blood pressure take a look at our AIC publication (pdf) that we presented in Tokyo in 2015.

UK favourite car colours

The top three favourite car colours in the UK in 2016 were white, black and grey (in that order). White has been the best seeing colour for four years which is interesting because it never used to be popular in the UK. Car salesman used to refer to the colour as three-week white because it took three weeks longer to sell a white car compared with other colours. But it’s 10 years now since a chromatic colour was number 1.

For further details see here.

colour and personality

Can you deduce personality based on colour choice?

A new quiz on playbuzz suggests so. You are asked to rate each of 10 colour palettes with either yes, no or not sure as to whether you like them or not. The test is created by Christina Yang.

I guess it’s just a bit of fun. It reminds me somewhat of the Luscher test, a colour-personality test invented by Max Lüscher. This test does have some credibility and is used by some psychiatrists. However, a number of papers recently published have caste doubt on its effectiveness. My feeling is that personality is probably too complex and multi-varied to be easily assessed by a few colour selections. Much the same could be said about horoscopes.

red rage in schools

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Staff at a primary school in Dundee want to change the colour of the uniform because they think the red colour could affect children’s behaviour. According to the Headmistress Gillian Knox:

‘Red is often used to energise body and mind, and some research indicates that it can increase heart and breathing rates. [This is] not the calm, relaxed learning state we hope to achieve. A recent study linked red to impaired performance on achievement tasks.’

Pupils currently wear a bright red jumper or cardigan with grey trousers or skirt. But teachers want there to be only ‘small amounts’ of red – such as in the school tie.

However, although statements such as this – that red raises heart rates – are all over the red and often cited as facts (as in ‘everybody knows’) in fact there is very little evidence that looking at red can affect heart rates. We ran a study at University of Leeds last year and found no statistically significant effect of the colour of light on subjects’ heart rates or on their blood pressure. A review of the literature reveals little evidence: there is a PhD thesis from California from about 1950 that nobody can get hold off and a study with mentally handicapped children in the 80s. That’s it. Light certainly affects us physiologically but it is far from fact that red raises blood pressure.

changing button colour increased conversion

button

It seems that only recently companies are carrying out what is known as split testing or A/B testing. Put two designs of a web site out and see which does best. Recently one company did just that. They had one web site with a green call-to-action button (as shown above) and another with a yellow call-to-action button. Changing the call-to-action button from green to yellow resulted in a 187.4% increase in conversions to their website. Is there some effect that yellow light could have compared to green? For example, could yellow light make users more impulsive?

According to Erika Dickstein it may be nothing to do with yellow at all but simply to do with the contrast – the yellow stands out better and therefore is more noticeable. Certainly more research is needed in this area.

Has technology for Harry Potter’s Daily Prophet just arrived?

I believe that print as we know it is dead. I know that there are some arguing that print is having a resurgence – just as there are those who think that vinyl is on the way back for music – but reports that physical books are gaining ground at the expense of digital are just plain wrong as is explained in this article. I saw this before with digital images where people argued that digital images would never replace traditional photography because of quality and price. Well, of course, we know that the quality of digital images increased and the cost of getting them decreased (when I was a student in the 80s it would have been bizarre to imagine that everyone would have a couple of cameras on them at all times) – but it was not this that killed traditional photography and eventually put the giant Kodak out of business. What killed traditional photography was when you could go to a gig, take a photo, and share it almost instantly with your friends around the world. Traditional photography could never compete with this.

Some people prefer reading print to looking at a screen though I am not one of them. But imagine when an e-document feels like paper, is light and flexible, but you can carry a whole newspaper with you (not to mention all the novels you have ever read) by carrying just one piece of it. And it looks just like print.

E ink, the company behind the pigment-based, low-energy monochromatic displays found in many of today’s popular readers has worked out how to create up to 32,000 colours using almost the same technology. For the first time they can create colours at each pixel using yellow, cyan, magenta and white pigments. The new display is 20-inch with 2500 x 1600 resolution. The image below is rendered in this way. This leads to the possibility of having coloured moving images made out of ink – just like the Daily Prophet in the Harry Potter movies. Well, not quite like that yet. But it’s coming. More details here.

ink

light that changes colour with your mood

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The future of lighting is LEDs and that means more colour. There are many advantages of LED lighting over tungsten or even fluorescent lights not least of which is the opportunity for more colour. I have noticed all of the new buildings on the campus at the University of Leeds are equipped with coloured lighting. The Laidlaw library – and even the new car park – is illuminated at night in an eerie purple glow.

The Syska SmartLight plugs into a standard socket but then can be controlled using the “Syska Rainbow LED” app for your Android or iOS phone or tablet.

I want one. But I am not sure they are on sale in the UK. More details here.