Kinetic weapon slot : White Ammo Energy weapon slot : Green Ammo Power weapon slot : Purple Ammo Just because the Kinetic and Energy weapon slots share the same weapon archetypes ( Auto Rifles, Scout Rifles, Pulse Rifles, Hand Cannons ) doesn't mean they'll behave the same way in the sandbox. There is a difference between the two. Some enemies are more respective to Kinetic damage and other will be more receptive to Energy damage ( like breaking through Cabal shields or shutting down Guardian Supers ).