To earn the Moss camouflage (makes you 100% hidden in mossy and grassy areas) you must sneak up to, and hold up (mug) The End (the old guy) and don't tranquilize him (or let him die by accelerating your system clock).

A good way in getting the camouflage and The End's tranquilizer sniper rifle is to hold him up first, then tranquilizing him. The Spirit camouflage lets you get close to The End without being detected; to get the Spirit camo, clear the level with The Sorrow in a previous game.