scarlet
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 color was early known (Genesis 38:28). It was one of the colors of the ephod (Exodus 28:6), the girdle (Exodus 28:8), and the breastplate (Exodus 28:15) of the high priest.
It is also mentioned in various other connections.
…The valiant men are dressed in scarlet… —Nahum 2:3 excerpt
…tie this cord of scarlet thread in the window through which you let us down… —Joshua 2:18 excerpt
A scarlet robe was in mockery placed on our Lord (Luke 23:11).
And they stripped Him and put a scarlet robe on Him. —Matthew 27:28
“Sins as scarlet” (Isaiah 1:18), i.e., as scarlet robes “glaring and habitual.”
Scarlet and crimson were the firmest of dyes, and thus not easily washed out.
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Answers about dye and dyeing in the Bible?