We're used to seeing Katy Perry with crazy blue wigs and her normal black locks -- but this week in Miami she had everyone seeing red!

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Katy stepped out to the pool on Tuesday with her newly-colored tresses and a cute pink polka-dot bikini ... but don't get too used to the color, it's not staying.

Perry tweeted about her hair change last week, saying "tonight I dye my hair a different color... Can you guess which color?!" before adding later "So I didn't get to the exact color I wanted from being black for so long! 2get to goal I have 2b GINGER for 3WKS."

Our guess: She's going blonde. Do you agree, or think she'll do something even more dramatic?

Check out the gallery above and see which other stars have gone red!