Parashas Metzora · Passuk 14:04
Chabad.org — English translation + Rashi
Torah Temima points to Toras Kohanim.
English: “And crimson wool” — if it said only “sheni,” any red shade might suffice; therefore it says “tola’as.” If it said only “tola’as,” other worm-derived colors might be included; therefore it says “sheni” — this is the fine scarlet dyed specifically with the tola’as.
Mi’ut / ribui pair
Chazal require the specific scarlet produced by the tola’as, not merely any red or any worm-derived color.