Scarlet

From BibleWiki

This dye was obtained by the Egyptians from the shell-fish Carthamus tinctorius; and by the Hebrews from the Coccus ilicis, an insect which infests oak trees, called kermes by the Arabians.

This colour was early known (Gen 38:28). It was one of the colours of the ephod (Ex 28:6), the girdle (Ex 28:8), and the breastplate (15) of the high priest. It is also mentioned in various other connections (Josh 2:18; 2 Sam 1:24; Lam 4:5;

Nah 2:3).

A scarlet robe was in mockery placed on Jesus (Mt 27:28; Lk 23:11).

"Sins as scarlet" (Isa 1:18), i.e., as scarlet robes "glaring and habitual." Scarlet and crimson were the firmest of dyes, and thus not easily washed out.