Blockland currently uses five datablocks for each colour. One for the spray can image ("weapon" in your hand), one for the projectile it fires, and three particles - spray, hit brick, hit unpaintable. 5 x 64 = 320.
This doesn't include the FX colours, each of which have 5 also. 9 x 5 = 45.
For just the paint can, that's 365 datablocks. The game can only handle so many, and each datablock takes a while to transmit. Do you want it doubled, tripled or even quadrupled so you can have 840 shades of red, green and blue while taking 10 minutes to load every single server?