Few questions about the physical basis of metals colours?

Question

I have a few questions about physical origins of metals colours:

1. What determines the colour of the metal (eg. yellow gold, rust-red copper and silvery colour of most metals)? I read on Wikipedia that the colour of a given element depends on relativistic effects that cause contraction or expansion of the orbitals, changing the value of the band gap, and makes the element reflect only certain electromagnetic waves, giving it the right colour. Is that right? Cause I'm not sure.

2. Can I change the colour of a particular element (eg. blue titanium, white iron, red nickel, etc.)?

Answer 1

I'm not sure. But I think, copper has its characteristic colour because it is the wavelength corresponding to "copper-colour" has least skin-depth, and is therefore reflected from the surface of metallic copper to reach the eye.