alternative grenade design

i was gonna do a search on tis first, but i couldnt think of a relevant keyword (C02 grenade? exploding grenade?) but i was thinking about a non harmful way to make a grenade actually explode.

why not put the paint in a bladder similar to the ones used on paint mortars, maybe a little tougher to survive being thrown around, and have a small C02 container connected to it with a tube running into the bladder. when you pull the pin it unblocks the tube running into the bladder and the C02 starts expanding into the bladder untill it bursts and sprays paint everywhere.

it seems simple enough to have been thought of before, so i was wondering, is there a reason it has been ruled out?

as far as cost goes, you could make the little C02 tanks re useable, you just go pick them up again after the game and re-fill it then attach it to another bladder. And i would think that a small C02 tank sraying C02 would not be much of a threat to anybodys health.

hmm, i c

mybe a re useable unit where you only replace the bladder? also running on compressed air rather than C02. the reg would be expensive, but as a re useable bunker buster, it could be worth it

:edit:

what about low pressure air or C02 or air with no reg? just enough to make it burst

  Yet another problem is that CO2 is really Cold.  I imagine that the co2 would freeze some of the paint inside and possiblly make it dangerous, but it might not. 

I can just see someone throwing a grenadethen saying "Crap! I foregot to pull the pin!", then some cocky kid picks it up, pulls the pin and the thing blows up in his face.