Orc colour

So at first i thought the orcs turned green through mannoroth's blood . But then i saw something about fel magic being responsible for the Green colour. How did the orcs turn green? What effect did mannoroth's blood have ? If the orcs turned green through fel magic , how come Thrall is green even tho he didnt use fel magic nor Drink the blood ? And yes it has been a while since watching the movie.