At an early age I made a light box (battery and flash lamp) and after lights out one night experimented with subtractive mixing various celluloid filters I had acquired. This experience is vivid in my memory - the joy of extenuating colours! My older sister had a friend who did theatre and I begged until he gave me a swatch book of Cinemoid gels, now one of my cherished possessions. In our lounge we have a light fitting and sometimes by slightly moving my head I can select any rainbow colour refracted in its "crystal" glass dangles: pure colour! Maybe that tells how crazy I am about colour. I have not yet met anyone with the same bee.
Primary colours
So many people and internet sites will tell you that the three primary colours are red, yellow and blue. This is so untrue! I have argued with artists on this one and they will not let go their preconceptions and yet I learnt as a child that blue and yellow did not always mix to give a decent green, and red and blue often gave brown rather than violet. When science told me the truth it was like a breath of fresh air. The reason RGB (additive) primary colours work is, of course, because that is how the human eye works. Ideally a primary colour filter should pass a reasonably narrow band of wavelengths such that superimposing a red, green and blue filter would cut out all light. The secondary colours cyan, magneta and yellow (as used in printing and sometimes called the subtractive primary colours) work for the same reason, but only if magenta is a pigment that reflects both red and blue, etc., so that when a magenta and say cyan filter are superimposed the net effect is the same as a primary blue filter. That would be in an ideal world of course.
Yellow
My nominally favourite colour is yellow. Is say 'nominally' because this is what I chose when I was a child and I have stuck with it, even though I probably love some other colours equally. But it has to be a particular shade of yellow. Most humanly produced yellows (paints, etc) do not do at all, indeed can be sickening. The yellow in a buttercup or dandelion comes close to my ideal. I have a hunch that the ideal is actually spectral yellow but I cannot be sure because I have never seen it. Although yellow, particularly yellow-towards-green, is the colour of the human eye's maximum sensitivity, the eye is incapable of seeing the spectral version in its full glory. It sees it only as a mix of response from the red cones and response from the green cones. Sad. But it is not only high saturation yellow that I love, I also love the liquid gold colours that one often sees in a sunset. So I suppose I am saying the colour must be vibrant or luminous.
Interestingly, on this subject Wikipedia says "Color practice technology is usefully contrasted with color theory science because science assumes perfect conditions, whereas commercially available products must deliver impressive results at affordable prices. In practical displays based on active-light pixels, compounding red and green point sources does not produce impressive and clear yellows. Thus, the next generation of TV and computer displays are starting to add a fourth "primary" of yellow, often in a four point square pixel area."
On the one hand yellow is associated with cowardice and deceit, on the other it speaks of joy and happiness. In the Bible there are few direct references to yellow and most are to do with leprosy which is bad. And yet gold, which is yellow's celestial counterpart, speaks of God in all his glory. The metal gold - why should it be commonly accepted that this metal is beautiful? - and yet it is virtually universally.
Check out http://totallycoolpix.com/2011/08/43-shades-of-yellow/ for some great photographs. Yellow is most effectively used both in nature and in art as a sort of punctuation or for highlighting. Consider dandelions on a lawn or buttercups in a field.
