Monthly Archives: February 2013

This is not yellow

A few people have asked me about this interesting and entertainig youtube clip – This is not yellow.

It’s worth looking at. It makes the point that when you look at colours on the screen (whether it is your computer screen, your TV or your mobile phone) although you see a full range of colours, all that is there is mixtures of red, green and blue light. In principle this is true – in practice it’s a bit more complicated because the screen doe snot emit just three wavelengths. For practical reasons the RGB primaries on a display are more broad band. Nevertheless, the essence of what is being said is true; when you look at yellow on the screen it is not a single wavelength that you would associate with yellow that is being emitted. Hence, the “This is not yellow”.

However, the clip doesn’t go far enough. It suggests that this is a problem with displays and that when you see a real lemon, for example, you are seeing real yellow because the lemon absorbs all the wavelengths of light except yellow (which is reflected). Sadly this is not true either. Let’s look at the reflectance profile of a typical yellow object. I can’t promise it is a lemon but a lemon would be pretty similar.


What this graph shows are the wavelengths of light along the x-axis and, along the y-axis, the per cent of each wavelength that the yellow object reflects. Notice that it does not absorb all wavelengths excecpt the ones that would be seen as yellow in the spectrum (essentially about 580 nm). Rather, the physical yellow object reflects all wavelengths in the spectrum because the reflectance is greater than zero at all wavelengths. The physical yellow object also absorbs all wavelengths in the spectrum to some extent because the reflectance is less that 100% at all wavelengths. Obviously some wavelengths are reflected more than others. But it isn’t even the wavelengths at about 580 nm that are maximally reflected. The yellow object reflects more red wavelengths than it does yellow wavelengths. So why does the lemon look yellow? For the same reasons that the lemon looks yellow on the screen; because the light being reflected activates the cones in the human visual system in a certain way. So I am not knocking this video – rather, I want to say that it makes a good point about displays but that this point also relates to colours in the subtractive world. It raises the issue of what we mean when we say something is yellow either on a screen or in the physical world.

colour and accessibility

Just came a across a superb article by Geri Coady, a designer and illustrator living in Newfoundland (Canada) about the importance of designers taking into account the fact that about 5% of the population in the world are colour blind. Well, it’s mainly men of course ….. but that’s all the more reason to take into account [joking].

Some really excellent advice about how to take colour blindness into account in design work. She talks about problems with the use of colour in London’s iconic underground map (see my blog about colour blindness and maps). She also comments on a game (Faster than Light) that has a colour-blind mode; I mentioned last week that SimCity was doing something similar. About time. It’s so lazy not to take colour blindness into account in the digital environment. There are also some great links to simulators.

skin colour and personality

Excellent article based on an extract from Nina Jablonski’s book “Living Colour: The Biological and Social Meaning of Skin Colour” about early ideas about the relationship between skin colour and personality.

The first scientific classification of humans, published by Carl Linnaeus in 1735, was simple and separated people into four varieties by skin colour and continent. Later, Linnaeus added that Europeans were white and “sanguine,” Asians were brown and “melancholic,” Native Americans were red and “choleric” and Africans were black and “phlegmatic”. Of course, these racist pronouncements were based on prejudice and myth and little, if any, factual information. Nevertheless, these ideas led to an intellectual foundation for racism. Immanuel Kant, was the first to formally define races and in 1785 classified people into four fixed races, which were arrayed in a hierarchy according to colour and talent. It sounds like a really interesting book on anthropology and I’ll order a copy tomorrow. I’ll try to remember to comment when I have read the full book.

Four temperaments is a proto-psychological interpretation of the ancient medical concept of humorism and suggests that four bodily fluids affect human personality traits and behaviors. The temperaments are sanguine (pleasure-seeking and sociable), choleric (ambitious and leader-like), melancholic (introverted and thoughtful), and phlegmatic (relaxed and quiet).

Red taxi

What is it about taxis that makes colour so controversial?

In 2009 I posted about the situation in Derby (UK) where the council introduced a new rule saying that all official taxis should be yellow and then got into trouble when they said that one taxi driver’s taxi was not exactly the right shade of yellow. How did they specify the colour?

A couple of years later there was a major political storm over a proposal for Durham (also UK – ooops …. embarrassing!!!) to adopt white as the official taxi colour.

Then in 2012 I wrote about taxi colour in Beijing. Well, this was not exactly news but by now taxi colour was starting to interest me!!

But guess what? Today, another genuine taxi colour story. This time it is in USA. The D.C. Taxicab Commission’s One Color Panel recommended Wednesday that District taxis be coloured red. Apparently, “Red is a color that is strongly associated with the District, both among residents and visitors,” the colour panel said in a statement. “The Stars and Bars of the District flag are red. Each of the major sports franchises in the District has a shade of red as a prominent part of the uniform. In the area of transportation, both the District’s Circulator bus and the Capital BikeShare vehicles are red.” All taxis will be required to change to the new colour within five years.


Eye colour and trust

According to a recent study eye colour plays a role in deciding how trustworthy others will think you are. Researchers simply asked a group of people to rate the trustworthiness of male and female faces. It was found that a majority of people found people with brown eyes to appear more trustworthy. This was true for both sexes but particularly so for men.


But it turns out that it is face shape that is more important and eye colour is a major factor because brown-eyed people tend to have certain facial characteristics. For the original story see here.

Colour qualification

Did you know you can get a qualification in colour. See Graham Clayton’s colour blog for more details. Graham is Chief Executive of the Society of Dyers and Colourists (SDC) and regularly blogs about colour. I am a Fellow of the SDC myself and have been involved in the organisation since 1982 believe it or not – more than 30 years!!!!