Colors of objects in white light

The color of an opaque object depends on colors of light  reflected by it.

An object appears white in day light if it reflects all colors. 

An object appears black if it absorbs light of all colors and does not reflect any color.

An object appears Red in day light if it absorbs all the colors of white light except Red, which it reflects.

An object appears Yellow in day light if it absorbs all colors except Red and green which it reflects. These combine to produce the effect of yellow.

 

What is color addition?

The mixing of coloured lights is called colour addition. When lights of different colours are mixed, different colour effects are observed.

Primary Colors are those which combine to produce white light and which can be used to produce light of all other colours.

The three primary colours are Red, Green, and Blue.
                     Red+Green+Blue = White
                     Red+Green =Yellow
                     Red+Blue=Magenta
                     Blue+Green = Cyan
The colours Yellow, Magenta and Cyan produced when two primary colours mixed are called "Secondary Colors".

The combination of coloured lights to give different colours is represented in below figure.