in grain adjectival phr. = dyed scarlet or crimson, fast dyed; hence in figurative use, esp. with contemptuous epithets, as ass, fool, knave, rogue…

Dyed in grain.

Dyed in grain: see engrain, v.1

Of a colour or dye: that will not readily fade or wash out; permanent. Now also in fast to: not susceptible to fading from.

Continuing without diminution or change; stable, constant, permanent. Of colours: permanent, unfading.

Dyed in grain; dyed with fast colours before manufacture; dyed in the fibre; thoroughly dyed.

Of a colour, photographic image, etc.: Fast, lasting, permanent. Said also of the photographic plate.

dyed in colours that will not readily fade or be washed out.

Dyed in colours that will not readily fade or be washed out; (also of a material or fabric) susceptible to being dyed in this way.

that can be washed without losing colour or dye.