It really depends on what looks best on your skin. Solid colors are great, but there are some cool prints too. Polka dots, colorful "Hawaiian" flower prints, sports themes, cartoon characters, whatever. Girls always have lots of cool options.
If you tend to be fairly white, pastel colors may look better on you, while if you're darker, then darker primary colors might be better.
Red. It's scientifically been proven to drive men crazy. Lighter colors as well, as they're more feminine, especially white (although, I wouldn't want to be wearing white during the middle of the month, if I were a girl)