I don't see greenish ones bud, only the brownish red ones are flatworms from what i can see.

i cant remember the name of that specific type but it is the kind that will not harm corals by eating them. but they can reach plague amounts and cover corals etc and shade them or smother them to death. Here are the animals that I personally have seen eat them.

Six Line Wrasse
Blue Velvet Nudibranch (exclusively eats flatworms but will die after they are gone)
Spotted Mandarin
Scooter Blenny