Did you know Kristen Stewart, star of the "Twilight" series, famous for her raven locks, actually has strawberry-blond hair? Scarlett Johansson, who we're guessing you know as a blonde, is a natural brunette. And Katie Perry? Also originally blonde.

How about your hair? If you can't remember what your hair's natural color (or texture) looks like, a new study published in the journal Carcinogenesis shows it would be a good idea — with a nod to Cindy Lauper — to let your true colors shine through.

Researchers looked at the hair product use data on more than 4,000 women and found that dark hair-dye shades were associated with a 51 percent increased overall risk of breast cancer, and a 72 percent increased risk of estrogen-receptor positive breast cancer among African-Americans.

The researchers think that it may be because darker dyes are more likely to be contaminated with chemicals such as endocrine disruptors and potential mutagens that have a destructive effect on cell genes.

Also high-risk for some: hair relaxers. Their use is associated with a 74 percent increase in breast cancer in Caucasian women, but not African-American women.

Go for both dark dye and hair straighteners? The risk jumps even higher.

So before you turn your tresses brunette, talk to your doc about your risk of breast cancer and whether it makes sense to avoid dark hair dye.

We also suggest that everyone consider avoiding chemical relaxers.

But if you do use one, know that the lye-based ones are considered most dangerous.