From Destinypedia, the Destiny wiki
Absorption Shields are a form of defensive barrier employed by various enemies during combat.
In battle, it manifests as a transparent bubble that surrounds the wielder. Elemental damage does inflict damage against certain types of Absorption Shields. The most obvious way to tell if a shield is weakened by a certain damage type is to see what color it is; for example, Fallen Captains with blue shields are susceptible to Arc attacks. Likewise a Vex Minotaur is susceptible to Void damage, and Wizards and Centurions respectively are vulnerable to Solar damage.
If one inflicts enough damage into a shield regardless of the color, it will deactivate, though this method takes longer, and may waste precious resources and ammo. A high impact weapon of sufficient destructive capacity can deactivate absorption shields in a single hit regardless of its elemental type.
Elemental grenades can take down shields of their respective element by simply detonating next to the target.
Shields gain a new appearance that varies between the enemy races: Fallen are unchanged, Hive gain more oblong and refined shields, Cabal shields are spherical with glowing angular patterns, Vex shields are cylindrical grids similar to the Hydra's, and Taken shields are blackened and "corrupted." Deactivating a shield with a weapon of its corresponding elemental type now triggers an area-of-effect explosion that damages nearby enemies.  Also, during Nightfall strikes and certain other difficult activities, the presence of elemental shields has switched between certain enemy types. For example, Psions no longer have Void shields during the Nightfall strike, but Colossi have Arc shields now.
Enemy shield types
List of appearances