Question

A white paper looks white because it reflects all the colours. Whereas though a mirror reflects all types of light it is not white. Why?

Answer 1

A white object reflects the light in all the directions, independently of the original direction. It is called a diffuse reflection. If you shine a beam of light onto a white surface, it is scattered in all the directions.
On the other hand, a mirror reflect the light symmetrically to the input direction, with no scattering. This is what allows us to see "through" the mirror.
That is why mirror doesnt appear white.