Reflection from surfaces

Question: The colour of any substance is that one which is reflected from it's surface. [I am not talking about hot bodies] but why is it that different colours are reflected from different substances?

Answer:

The ability of a surface to reflect or refract light depends on the interaction between the light and the surface.

As you know light is an electromagnetic wave, that is a magnetic field and an electric field oscillating at right angles to each other. It is the effect of the field produced by the atoms of the material on the light that affects its path. The interaction is explained (!) by considering Maxwell's equations for an electromagnetic wave and these are frequency (and hence wavelength) dependent. Therefore the effect of different surfaces on different colours of light can be predicted.