Why is it that whenever I drink grape juice, my lips get stained a brownish purple color?

this will not go away either, I just have to wait until it fades off or until I eat somethingWhy is it that whenever I drink grape juice, my lips get stained a brownish purple color?
Their is Tannin in the grapes not dyeWhy is it that whenever I drink grape juice, my lips get stained a brownish purple color?
because there is dye in the grapes that dyes your lips