if they did use grenades, i think it would be normal frag. seeing as how, for the most part, we havent really seen any forces making active use of body armour on a regular basis, it would probably be the most efficient and cost effective method

i also believe the chameleons themselves are somewhat shielded from energy blasts, so i cant see them making an energy grenade since it would only be effective against certain targets

also, do they really need grenades? any advantage that a grenade could possibly make is surely trumped by their chameleons and superior training

In the Warhammer 40K universe, the Imperial Guard's rifle and side arm, (the Lasgun/laspistol) are powered by batteries that can have the internal peices absorb light and heat, and focus the energy through the laser. In fact, they can toss a spent battery on a fire to recharge it really fast, thought that weakens the battery and increases the chance of malfunction.

It's pretty nifty, if you ask me.