Nobody can say that Baremettle are not trying their best to appeal the girls
In a medieval world, pink should be one of the most common colors amongst the working class. You're talking natural fiber cloth, most of which is going to be beige or brown to start with unless somebody takes the time and expense to bleach it somehow. Then your talking natural pigments, nearly all of which are water-soluble so fade quickly, don't come in every color, and the availability of certain colors varies widely. In the real world, red was common and cheap whereas purple was rare and expensive.
So say you've got some coarse homespun that's naturally a sort of brownish color, and dye it with cheap red pigment. Then you work up and sweat in it, or are out in the rain or even just prolonged exposure to UV light. Before too long, your clothes will be some pinkish shade.