Let's be frank. Obama is black, Bill Clinton is white, and any black or woman running for President has much higher hurdles to overcome, and biases to break through. I don't see Obama or Hillary as having an especially easy time doing that. As far as being black and running for President, Colin Powell would have a far easier time than Obama, IMO, because of his experience, even taking into account how anti-GOP the press is.
I don't think this is true any more. I think there are as many people who would love to see a minority or woman president as there may be some old-timers who shudder. Pop culture worships the minority of all kinds these days. Why else would "Will and Grace" have been so popular?