TT #270 · Parshas Tazria · Aliyah 7 · Passuk 49
English: and the lesion is greenish or reddish in the garment, leather, warp or woof, or any leather article, it is a lesion of tzaraas and shall be shown to the priest.
Torah Temimah cites Sifra (Toras Kohanim) for limiting the color rule to the specified greenish and reddish shades.
Sifra — Vayikra 13, Midrash Sefer
English: Might every shade of green or red qualify? The verse specifies greenish or reddish.
Textual derivation
The Torah’s terms “greenish” and “reddish” refer to the specified qualifying shades, not every shade that could be described as green or red.