I once dissolved sodium bromide in a concentrated HCl-acidified solution of copper(II) chloride. The solution turned brown as a copper(II) bromo complex was produced. When diluted with water, a dramatic color change occurred, ultimately forming blue copper(II) aqua ions (blue).
Copper forms a variety of interesting complexes. Here is more information from woelen's website: http://woelen.homescience.net/science/chem/exps/cu-redox/index.html
Complexes of copper(I) often assume strange colors. I recognized the yellow color of the copper(I) oxide as the one produced when copper objects are electrolytically oxidized in aqueous sodium chloride solution.