Chameleon is a gear perk that slows how quickly enemies detect you without changing how suspicious they get. It buys you extra time when a guard starts to notice you.
When a soldier starts spotting you, the detection meter fills more slowly, giving you time to break line of sight or take him out.
Wear one of the gear pieces that carry it: Dark Tech Hoodie, Londoner Swag, Tea Time Jacket. Each piece only takes one body slot, so plan around the other perks you want.
Yes for stealth builds. It is one of the most forgiving stealth perks in the game.
Pairs well with Assassin and a quiet Amigo like Chorizo or Oluso.