The bronze MEDALS are largely copper because burnished bronze and gold are similar in color, and the mint did not want any confusion as to which medal an athlete receives.
As an experiment, I have questioned husbands of long standing about the color of their wives' eyes, and often they express embarrassed confusion and admit that they do not know.
Now think of that other person palming the mouse, surfing YOUR site. If your website is a frenzy of color and confusion, all it takes is one CLICK and you're forgotten!