**note you must have spoken to the guy at the albino exchange before you can get this achievement. his location is up the stairs near the forgotten entrance.**
The first albino i came across was in the armory room while doing the access base armory mission for the forgotten. as you enter the armory room, turn right and its hiding in a vent next to a sign at the end of the room, switch to you pistol and make sure you have the secondary ammo (yellow) equppied then tag it.