Question

Why do metals have lesser colours than non metals

Answer 1

This is a good question, eventhough metals are shiny (lustrous) , most metals are grey or silver. Colour diversity is less.
Why metals are like this?
Reason is that these metals reflect almost all wavelengths.{as we know reflecting almost all wavelengths means colour will be more like whitish}
Detailed Explanation
This is because they have lots of free electrons (that also happens to be why they're good conductors). When light (electromagnetic radiation) hits the surface of a metal, it moves the electrons in the metal up and down, up and down. Because moving electrons re-create electromagnetic radiation, the wave of radiation is re-transmitted more or less perfectly back away from the metal again.

A coloured metal like gold has most of these properties, but it absorbs just a little bit of radiation in the green-blue-violet area. So whatever it reflects out has a bit of green-blue light removed and the result looks (by subtraction) yellowish red.

Metal like silver (e.g., a mirror) reflects all wavelengths specularly (the reflected rays bounce off nicely).
A metal like lead also has most of these properties, but it absorbs a little more of the entire spectrum, so it looks grey.