Tag Archives: yellow

changing button colour increased conversion


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.


What colour is your office?


I just saw an interesting article by Kim Lachance Shandrow about how the colour of your office can affect productivity. The article refers to a paper (2007) in Color Research and Application (CRA) by Nancy Kwallek entitled Work week productivity, visual complexity, and individual environmental sensitivity in three offices of different color interiors. The paper suggests that the influences of interior colours on worker productivity were dependent upon individuals’ stimulus screening ability and time of exposure to the interior colours. CRA is a top quality academic journal that is peer reviewed and so I am respectful of the findings.

However, in Kim’s online article there is a lot of stuff that I am highly sceptical about. For example, she writes that “Red … increases the heart rate and blood flow upon sight.” Is this true? Is there really any evidence for this. I have two PhD students working in this area right now and I am far from sure that colour does affect heart rate and, if it does, the effects are probably tiny. And yet we can read statements like this all over the internet as if it is a fact beyond doubt. Other things she says that I take with a pinch of salt is that “green does not cause eye fatigue” and that “yellow triggers innovation.” Don’t get me wrong – I am very interested in how colour can be used to affect us emotionally, psychologically and behaviourally; it’s just there is a danger that if some things are said often enough (such as red increases your blood pressure or heart rate) then people start believing them even though there may be little evidence.

That said, you might find the infographic fun and it is well done. See the original and full article here.

eyes change colour?


I didn’t realise how sophisticated reindeers are. It turns out they have two layers of fur to help them keep warm, are able to shrink the pads on their hooves to give then better grip, and can detect ultraviolet light which enables them too see in very dim light. And it also turns out that their eyes can change colour in winter so that their vision is more sensitive. Reindeers, like cats, have a reflective layer behind the retina (which is the inside of the eye ball where all the light-sensitive cells are) that helps them to see in dim light. This is why, if you see a cat at night, you might see the eyes shining; you are seeing light being reflected back at you from the cat’s tapetum lucidum (which is the technical term for the layer behind the retina). The light that shines back in most animals with this layer is golden but in reindeer it apparently shifts to blue in the winter. The shift to blue allows more light to be scattered and improves the vision of the animal.

The full paper can be read in the Proceedings of the Royal Society.

Where is colour mixing?

Imagine that we have three projection lamps at the back of a hall – one has a red filter and so produces a beam of red light, and the other two use filters to produce green and blue beams. We project these onto a white screen and get three circles of light (one, red, one green and one blue). We then move the angles of the projectors so that the circles of light overlap. We get something that looks rather like this:


Where the red and green light overlap we get yellow. We get magenta and cyan for the other two binary mixtures. So,

red + green = yellow

red + blue = magenta

green + blue = cyan

This is called additive colour mixing as I am sure you know. And if we mix all three primaries we can achieve white (or other neutral colours). The primaries could be single wavelengths of light – so we could use a primary at, say, 700 nm (for the red) and one at 450 nm (blue) and one at 530 nm (green). So green light (530 nm) and red light (700 nm) additively mix together and generate yellow. When this happens what is being mixed and where does this mixing take place? Take a few moments to consider this before reading on.

Notice I said that they additively mix to generate yellow – I specifically avoided saying that they mix to generate yellow light. When I sat down with a couple of students last week and asked then what they though they said that the red and green light mixed together to create yellow light and when I pressed them, they went further to say that the yellow light was at about 575 nm.


If we measure the part of the screen that is yellow we would see that we have some light at 700 nm and some at 530 nm. The wavelengths are not mixed; they don’t mix together to generate some third wavelength of light such as 575 nm. So no physical mixing takes place other than – I suppose one could argue – that the red and green lights are mixed in the sense that they are spatially coincident. But that’s not really mixing, for me, and certainly doesn’t even begin to explain why we have the sensation of yellow when we look at these wavelengths together. It also makes me think that additive colour mixing, if it can be said to occur anywhere in particular, occurs in the eye. And I do mean eye, not brain.

why I don’t like the colour wheel

There are many reasons why I don’t like colour wheels of the type shown below:

The first reason is because it perpetuates the myth that the subtractive primaries are red, yellow and blue whereas the fact is that red, yellow and blue produces a rather small gamut of colours. It is certainly not the best choice of subtractive primaries though it is taught as dogma in many art and design schools and throughout children’s education. The problem is that whenever two colours are mixed together there is saturation loss; that is, the resultant mixture ends up being more desaturated than the two components were. The saturation loss is greatest when mixing colours on the opposite side of the colour circle where the resultant mixture can be almost grey. However, for certain choices of primaries, the saturation loss is greater than for others. If red, yellow and blue are used as the primaries then of course it is possible to generate any other hue. However, there is significant saturation loss and the above colour wheel gives completely the wrong impression. It suggests that mixing blue and yellow together, for example, results in a really bright vivid green.

The reality of pigment mixing is much more like the triangular colour wheel shown below:

In the above diagram it can be seen that mixing together yellow and blue results in a really muddy dark green. The purple resulting from mixing blue and red is almost black!! Now it is possible to mix together a blue and a yellow to get a better green. For example, mixing a greenish blue with a yellow will give a much more vivid green. Mixing a bluish red with a greenish blue will result in a lovely purple. We have a name for a greenish blue and a blueish red – we call them cyan and magenta. A much better colour gamut is obtained if we start with the primaries, cyan, magenta and yellow.

Footnote: Some people may look at the triangular colour wheel and think that the reason the colours are dull is that the red, yellow, and blue primaries used are not ‘pure’ enough. Nothing could be farther from the truth. If it was possible to make really vivid and bright red and blue pigments then the resultant colour gamut would be even smaller. Fundamentally, red, yellow and blue just don’t make good subtractive primaries.

yellow is the new red


I am not the world’s expert on fashion but it seems that red has been popular all through spring and summer. I first came across the surge in popularity of red last year when a journalist contacted me to ask my opinion as to why there had been an increase in sales of red kitchen and personal electronic equipment. We both agreed that probably the choice of red may be caused by consumers using colour choice to be bold and energetic in contrast to feeling tied down and depressed by the financial recession. I then listened to the podcast for Spring 2011 on Color Outlook and learned that red has been a popular colour for interior design this year right across the USA.
Now it seems that red has been a popular fashion colour all summer but is due to be replaced in the autumn (or the fall, as some people strangely call it) by yellow; another vibrant and positive colour. For further details see the Babble blog.

preferred colours

Many studies have been carried out over the last 50-100 years to look at which colours people like and which they don’t like. Although there is variability between individuals (not everyone likes the same colours) there is surprising consistency when the results of lots of different studies are compared. In short people like blues and greens and don’t like yellows and (to a lesser extent) reds. The hue parameter is probably the most important but brightness and colourfulness also affect colour preference. People tend to like brighter and more colourful colours than darker and less colourful ones. Just for fun, I have been running my own survey on this web site. You can still add your two-penneth worth if you like – please go to http://colourware.wordpress.com/2011/02/22/favourite-colour-poll/. Interestingly, my fun survey is also in broad agreement with all those previously published experiments. I found that people’s preferences were:

blue 19%
green 19%
purple 14%
red 11%
orange 8%
yellow 8%
pink 8%
black 4%
grey 4%
white 3%
brown 1%
other 1%

I am not sure what practical application there could be in knowing which colours are more popular. For example, my favourite colour is red but I probably wouldn’t want to buy a red coat. Though on average most people really like blue, this doesn’t mean it would be sensible to make a product blue without consideration of many other factors. In design, colour is almost always in context and that context makes all the difference in the world.

More interesting though is recent research I have read which proposes a reason why there is individual variation in colour preference. According to this idea, we like those colours that remind us of things that we like (we like blue skies and green grass). It could explain dark yellows and oranges are particularly unpopular; these colours are normally associated with some rather unsavoury things (dark orange is the colour of poo and dark yellow the colour of vomit). Further, if people have a strong affiliation with an idea/concept that is strongly associated with a colour, then they may have some preference bias towards that colour. It makes me think – I am a hug fan of Manchester United and red is my favourite colour; but do I like red because I like Manchester United or do I like Manchester United because I like red? I am too old to remember which came first.