Usually, the color white is associated with purity (as indicated by the kittle). I don't know if the opposite color in the spectrum represents the opposite of purity (yes, I know it's not technically the opposite, but is perceived as such); but if the purpose is to dress in a modest way that does not attract attention, there are certainly better colors than black, which seems to be the most frequently worn color in the female Jewish world (based on my unscientific study of looking around every day). This is especially true at joyous functions like a wedding. Why wear a somber color at such occasions? Furthermore, black is generally seen in the fashion world as a slimming and elegant color, so assumedly it would actually attract more attention than say a nasty brown or gray, thus defeating the purpose of wearing it to be more tznius.
So I ask again, why do women overwhelming favor black clothing?