Why do blue and yellow pigments create green when mixed?

[Chemist@]

Why when artists mix blue and yellow colors, we see green? What is the physical explanation of this?

 

[mathman]

Interesting contrast: mix red and green light and get yellow or orange.

 

[Drakkith]

Why when artists mix blue and yellow colors, we see green? What is the physical explanation of this?

The combination of yellow and blue light stimulates the cone receptors in our eyes in about the same way as pure green light does.

See here: http://en.wikipedia.org/wiki/Color_vision

 

[Chemist@]

So there are three different types of vision receptors for the three basic colors (Young–Helmholtz theory). What must be the distance between two substances e.g. one blue and one yellow colored so we see it as green?

 

[Drakkith]

So there are three different types of vision receptors for the three basic colors (Young–Helmholtz theory). What must be the distance between two substances e.g. one blue and one yellow colored so we see it as green?

I can't say since colors are subjective. There is no wavelength that we could single out and say, "This is green" or "This is blue".

 

[sophiecentaur]

So there are three different types of vision receptors for the three basic colors (Young–Helmholtz theory). What must be the distance between two substances e.g. one blue and one yellow colored so we see it as green?

There is a huge difference between how we can mix different colours of light (synthesis) and how our eyes actually analyse colours. The response of the eye is not really to three colours; the responses of the three sets of sensors are very wide band- corresponding to red(isn), green(isn) and blue(isn). A single monochromatic source may well stimulate all three sensors. However, it is possible to mimic the perceived colour of an object by using three, very narrow band, sources. The three (RGB) phosphors, used in colour TV are narrow band (as narrow band as is compatible with making them bright enough, actually). To sum up - analysis is broadband and synthesis is narrow band.

The above quote, refers to subtractive mixing of colours, using pigments or filters, which is totally the inverse of mixing colours using light sources. Pigments work by absorbing certain colours. Mixing two colours of pigments will produce a result which only let's through or reflects wavelengths that the two pigments will each let through. Printer inks (Magenta, Yellow and Cyan) are usually thought of as 'Minus green', 'Minus Green' and' 'Minus Blue' and 'Minus red', respectively. (Or R+B, R+G, or B+G)

Or are you referring to the spatial discrimination / acuity of the colour receptors on the retina?

Also, incidentally, a grid of blue sources, interspersed with yellow sources will look white (or, at least, neutral grey) because Yellow corresponds to R+G and White corresponds to R+G+B.

 

[sophiecentaur]

Using the sliders on the colour controls on your computer drawing package will show you how additive mixing (synthesis) works. Fun and instructive at the same time.
Using a kid's paintbox will show you that mixing pigments takes progressively more and more light away (subtractive mixing) and you always end up with a sludgy dark grey as you mix 'contrastin'g colours - i.e. ones that do not share common spectral components.

It is a good idea to avoid using the words Colour and Wavelength as synonymous terms. They are not the same thing at all.