I was always of the understanding that white light was made up of red, yellow and blue elements. Any other colour could be created using these three primary colours. It made sense that blue for example turned to orange on a negative and yellow turned to purple, and the negative of green is red. Why then (does anyone know) do cameras, monitors, scanners projecters etc. use green instead of yellow, whats the point of adding blue to yellow to make a green element when it can be created anyway in the same way as i.e. orange. Why yellow/blue? why not have for example have PYB (Purple Yellow and Blue). I think what I'm trying to ask is why is yellow not used as a primary colour, there must be a reason for it, but I can't work it out and its bugging me now!

Attached Link: http://en.wikipedia.org/wiki/RGB

Thanks for the link, almost imedietly it refers to green as a primary colour....since when? Its a secondary colour surely....anyway back to the link..

From the link ... "Many will insist that red-blue-yellow are the "primary colors" in an absolute sense because no combination of other (subtractive) colors will produce them. However, in additive color, red + green = yellow and no simple combination will yield green. In this sense red-blue-green may have the truer claim to being absolute primaries, since additive light works with color directly from its originating source (light). It should be noted that additive color is a result of the way the eye detects color, and is not a property of light. There is a vast difference between Yellow light, with a wavelength of approximately 580nm, and a mixture of red and green light. However, both stimulate our eyes in a similar manner, so we do not detect the difference." Sort of starts to explain it, great help! Thanks Richard

Well I have good news for you. Due to a discovery by one of your fellow countrymen in the 19thC it was found that by shining lights of red green and blue light onto a surface that white could be formed and that the overlapping areas would form Yellow, Magenta, and Cyan. From this discovery stemmed colour photography. The question of why Yellow? I think can only be answered by: It works ! Perhaps a finer study of the gentleman's work will reveal his exact thinking of why he tried these colours, but I know they were not the first colours he tried. The gentlemans name: James Clerk Maxwell

Another thing I picked up is the concept of ADDITIVE and SUBTRACTIVE colour mixing which is new to me. Still its interesting what can be picked up from a quick search on the net.

Interesting Question Anthony, never even gave it a thought, interesting thread and link too, that link btw takes you miles into other related issues and has answers some good questions.

Yes of course, additive or optical (light) mixing is in many ways the opposite of subtractive ink or paint color mixing. In optical or additive mixing, the 'primary' light colors combined give white light; in subtractive or ink color mixing, the combined primary color mixing gives black. When we talk about primary colors in subtractive color mixing, we talk about magenta, yellow and cyan, the pure colors. Additive color mixing uses exactly the colors in between these three primary colors: magenta and yellow give RED; yellow and cyan gives GREEN; cyan and magenta gives BLUE; hence 'additive' color mixing. RED, GREEN and BLUE, or RGB, or the colors used in light mixing technology.

Red, yellow and blue are the prim of light bu tthe prim of colour (art/film/eyes...) are Red, green and blue. Don't know who made the rules but when I learnt about it at like 12 it was a shock to me too. I learn why in Physical Science at school but that was 6 years ago and now I've forgotten... But any who...

To make it all even stranger, in broadcast colour television (ntsc, pal, don't know about other formats) the green carries all of the gray scale information.