Why are niqabs/abayas are usually black?

I'm not an expert on this matter but is there a requirement of some sort regulating the color of the outfit. I rarely see any other color than black and I'm not talking about localized variants of the clothing. Given that black absorb more heat than many other colors, it would seem to be counter-intuitive for such a color to be so common in a hot environment from where niqab/abaya claim to be originated from. Does the color have any significance to it? If so, is it cultural or cited in Islamic sources?