I am afraid that if that is true seal could be already painted in all shades of red - to advertise poison seal, dragon fish patter or grey to disappear completely.
Unless they didn't have evolution al time to develop that skills.
On another time octopus had and still don't know how effective it is since that is the favourite snack.
Anyway any innovation welcome if works

Much better could be suit imitating their own species, specifically opposite gender, to provoke less aggressive behaviour, unless they are cannibals

The wost of all could be Mantis Shark that f** you first then eat