Beanie

The Clothier only offers this while he is living in a snow biome house, so you either build him a room up in the tundra or move him there for a visit and shift him back after. His stock follows the biome he sleeps in, so make one trip and clear out everything the snow list has rather than moving him twice.

It is nearly colorless, so ordinary dyes barely register on it. Combine with black dye or reach for one of the strange dyes if you want a result you can actually see.