Basically, mehndi / henna is a translucent stain. If your skin is dark enough that your palms are lighter than the backs of your hands, your palms will take mehndi / henna easily and beautifully, with excellent contrast. On the rest of your skin, the mehndi / henna will stain in the range of dark amber-red-burgundy-rust or brown color. On darker skin, bold patterns are more likely to show up well than the filigree work that shows up easily on pale skin.