How do you get stealth camo in Metal Gear Solid 2

Play through the game a few times on the same save file and get dog tags.
You can get dog tags by holding up a soldier who has one and aiming at their head. The ones who refuse; just shoot them in the arm or between their legs to "convince" them. If you equip the camera/scope and hold triangle, you can see the names of the guards whose dog tags you have. It takes about 3+ playthroughs on different difficulties to get it.