Parashas Metzora · Passuk 15:03
Chabad.org — English translation + Rashi
Torah Temima points to Toras Kohanim.
English: “It is his impurity” — from here [we learn] that the impurity of the male is through white [discharge] and the impurity of the zavah is through red.
Gender-specific colors
Chazal establish the classic distinction: white for the male zav, red for the female zavah.