Zhora's tattoo

Has there ever been an actual explanation for Zhora's magically appearing tattoo? I was surprised it wasn't addressed on any of the commentaries (none that I heard, anyway). It would make sense if it was covered with some makeup that washed off when Zhora showers . . . but we don't actually see it appear in the shower. It only appears when she dries her hair. Is it heat activated? I can't imagine this being a continuity error (if it is, it's the most blatant continuity error of all time). So if it isn't, I'd think there would at least be some explanation for why it suddenly appears (like, showing her wash away makeup in the shower would have been one way). Any ideas?

I understood that she hides her tattoo during her show with the snake but lets it after the shower because it's her private style. I'll try to make a nice gif animated showing it. Her skin and silhouette are wonderful too. She could have made a film about the amazons with this look of Penthesilea.