Shifting Pearlsands Dye

This is the pink relative of the plain shifting sand dye and the two are close enough that it is worth holding one of each and looking at them on the armor you actually wear before you commit. The pale one washes out against light colored sets. The pink reads clearly against white and gold gear, which is most of what a Hallow themed loadout looks like.

No shop sells it and no crate contains it. Crafting is the only route in, so the gate is having the dye vat up and the materials in hand rather than any particular boss being dead.