The color systems used by scientists and artists are totally different.An artist will mix blue and yellow paint to get a shade of green;a scientist will mix green and red light to create yellow.The printed page in a magazine is yet another system.
Now,lets seperate the two different kinds of color in the world.First,there's the color you can touch,such as the skin of the apple or a painted wall.These colors are part of the surface of an object.Next,there's the color you can't touch,such as a beam of light and the colors produced by your computer monitor.Colors generated by light are part of a color system.The tangible colors which are on the surface of objects or on the printed page are another color system.
Additive colour mixing
Additive colour mixing is the reproduction of any desired colour by adding together different amounts of just three colours,red,blue and green,which are called the additive primaries.
This is how the colours in TV pictures are produced.The back of a TV screen is covered with a regular array of dots of three kinds of materials called phosphors.One kind glows red when an electron beam inside the TV tube hits it.The other kinds glow blue,green,respectively.
Purple is created by stimulating the dots that glow blue and red.Yellow is created by red and green glowing dots.White is created by a mixture of red,green,and blue.
Subtractive colour mixing
Subtractive colour mixing is used in photographic transparencies and prints.Such pictures are made of transparent layers,each layer partly clear and partly coloured with one of the subtractive primaries-magenta(red-blue),cyan(blue-green),or yellow(a combination of red and green).White light shining on the picture is a mixture of red,green and blue light.In this print industry,cyan,magenta,yellow and black are used as the primary colors.When you mix all the colors,the result is grey.