Dyer

Someone who dyes cloth or other materials.

"The man who cannot distinguish the false from the true/

Sustains as heavy a loss and blow to his heart/

As the 'expert' who thinks he can tell the two dyes apart/

When he can't tell Sidonian blue from the similar hue/

We get from the moss of Aquinum and use for our cloth."

Horace, Epistle to Aristius Fuscus (21 B.C.)