Chlorophyte Dye

The green here is the same sickly shade the ore has, and the part that matters is that it keeps showing when the light goes. In a dark cave or against a night sky, a dyed set reads as a moving green outline instead of a dark blob. That suits wings, capes and hoods far better than it suits a detailed chest piece.

It does not light anything up. The glow is painted on the sprite, so it will not save you a torch.

The Dye Trader only starts offering it once a mechanical boss is down, and only in exchange for Strange Plants. Collect those while you are already crossing the surface jungle on Chlorophyte runs rather than making a separate trip for them.