Most Helpful Guy
Darker colors. No yellow or orange. I like blues and greens, sometimes red or even black.
If you have non-brown eyes (and I assume you do, if you have blond hair) get something that matches your eyes. I know, weird, but people subconsciously notice it.
More important is the cut. Make sure it's flattering to your body type. If you're skinny, don't go for the one-piece; it'll look pre-pubescent. On the other hand, if you're curvy, don't go for the super skimpy thong and barely there top.
But you probably knew that already
Best of luck, and if you have a good friend, ask her to pick out a few for you to try on. don't pick your own and then ask her if it looks good; she's liable to say yes if you really like it, even if there's a better one for you. Have her choose.