Blue Acid Dye

A dark blue ripple pushes outward across whatever you dye, in the same family as the other two acid dyes. The useful quirk is that dyed gear stays visible in unlit areas without emitting any light of its own, so you can pick your own character out of a pitch black cave while your torch stays in your pocket. It is close enough to Gel Dye that the two are easy to confuse in a screenshot.

Getting it is luck. Strange plants go to the dye trader and he hands back whatever he feels like, with no way to ask for a particular color, so building a matched set means a lot of plants.

Any of the acid dyes on a Shadow Orb will make chunks of it disappear, which is either a bug or the best looking accident in the dye list. Acid Dye and Red Acid Dye do it too.