The JP version is a tiny bit off too. (Odd, Pin.s' Japanese is usually very on point, enough to pass for a native's.) Enough to make me doubt whether I'm reading it correctly, but checking with the Chinese version shows it just means what it literally means. Same goes for the English version here. Pin.s is interpreting Swantsuki's hair as being multi-toned (instead of reflective shadings/shadows to distinguish silver hair from white), with black (and purple) streaks/gradients near the tips. Hence "dyed" by Hatsuducky's colors.
(That said, the grammar in the EN version is technically perfect. The choice of the words "variegated", "soiled", and "stained" are also brilliant and precise [especially coming from a non-native English speaker]. It's just that the text sounds unnaturally awkward, so most people will doubt whether they're reading it correctly.)
