Color theory basically deals with the relations between colors, how they interact, and what effects they give when put together.
Nothing to it. Kodak used to have a book on this. You can look for any book on colour printing or processing and there will be a section on colour theory.
In photography, there are only 3 primary colours for light, Red, Green and Blue and when you mix them you get white. This is because the eye is sensitive to these 3 colours and any colours in between is mainly deciphered by the brain by the proportion of the light that is sensed by each of the cones in the retina sensitive to R, G and B respectively. The colours are additive.
Secondary colours are obtained by mixing 2 primary colours. Yellow=red+green, Magenta=red+blue, Cyan=blue+green.
For prints, the colours are subtractive because light is being absorbed. For example, a red colour absorbs blue and green from white light, only red is reflected, that why you see red. So if you mix red and blue pigments, you don't get anything left because blue pigment absorbs red light as well.
So for prints, usually secondary colour pigments are used because each only absorb a primary colour. Eg magenta pigment absorbs green, reflecting only red and blue. Yellow absorbs blue and cyan absorbs red. If you mix magenta and cyan pigment, you'll get blue since both reflect blue light, red is absorbed by cyan and green is absorbed by the magenta.
Books for videos and TV might also have such a section because the phosphor used in CRTs are RGB also.