When I played paintball, we used surgical tubing injected with paint and tied off with a rubber band or ziptie. Total cost: about $.30 per grenade, they sprayed on impact 3 times out of 5.
You could make a Co2 powered one I suppose, that uses 12gram powerlets, other than that I can't say I have any more advice.
Every word ever written will fall short, of it's intent
Even sung, or spoke, or screamed, they will betray what they had meant.