[NorthFrost]

I've only just started this topic, so I'm sorry if the answer to my question is obvious!

From what I've learnt so far, colours in transition metals are largely determined by the difference in energy between the d split levels - an electron will be promoted when it absorbs a light frequency of energy equal to the difference in energy between levels. With the d orbital full, electrons can't be promoted, no frequencies will be absorbed, and light will be unaffected (no change in colour).
If any of this is wrong, please tell me .
Assuming it's right, how come Cu is that namesake copper colour? Isn't its d orbital full? Or is the d orbital sometimes at 9 - is the 4s electron not always promoted to 3d?

[Borek]

colours in transition metals are largely determined by the difference in energy between the d split levels

As far as I remember what you wrote is about colors of compounds of transition metals, not of the metals themselves.