[scifan]

 If a complex appears red-violet, what colour light does it absorb?

[Dan]

Please show an attempt at the question, or at least demonstrate that you've thought about it. Forum Rules.

Think about tinted sunglasses - if they have a red tint, what colour of light do they let through, and what colour(s) do they absorb?

[cheese (MSW)]

Hint: [Cu(H2O)6]^2+ (as in a soln of CuSO4) has a broad absorption (d→d transition) that just makes it
to the red region...    If you get a chance flash your red laser pointer through such a soln.
and also through one of Co(H2O)6}^2+.  google complementary color (it is not a straightforward topic).