Colors from candidates' websites
I've made no effort to ensure that the sites I'm referring to are the official candidacy sites for the candidates. I went to Google and punched in (for example) bush 2004 and took the first reasonable hit. (I had to make a judgment call about reasonableness when it came to Al Sharpton, but as near as I can tell http://www.al2004.org is the current site.
I've also made no attempt to represent the prominence of each of the colors on the site - they're just the colors that jumped out at my eyedropper tool.