58 I just wasted a bunch of time derping around with the Paintslinger lens on a Mana Blaster from Botania.
Turns out that if you craft it with a Mana Pearl to give it a rainbow tint, it'll turn any wool or stained clay (or probably some other things that I haven't tested, like stained glass and sheep) connected to the one it hits within an ~18 block radius a random color. However, the connected blocks have to be the same color in order for it to work- so if you shoot it at an area that's already been randomized, it'll usually only change one block.