When enraged sayotsu's eyes turn red which is not sharingan this is his awakening of dark side which unleashes huge amount of chakra,sayotsu looses his mental state and begins to destroy every thing,his physical strength and speed increases drastically also his chakra reserves increases.In his state of dark side he looses control over himself he becomes like a tailed beast however once the darkside runs out it leaves sayotsu weakened.The advantage of dark side is genjutsu doesn't work on sayotsu when he is in his dark side state also his endurance increases beyond human limits. The Dark Side a seal is one of the strongest cursed seals. Similar to Sharingan, which, when activated,has red eyes and spread through out the user's body. Like all cursed seals, the user receives increased chakra l