White Voodoo hardly increase yours Defense Level,but decrease your Attack Level /that means increase your phys and elemental defense,but decrease yor phys or magical attackBlack Voodoo hardly Increase your Attack Level,but it decrease your Defense level/so that mean you hit harder,but your defense is going low/down, and you die faster
Psychics always change state depending on the enemy. If a psychic is fighting a sin per example, he will go white voodoo until assassin's tidal run out then stun assassin and thingies, go black voodoo and rape the sin. So yeah, psychics always change state depending on the foe they're fighting.
White voodoo is a tank mode,look at is as a sage barb true form. Psys use it to tank,so psy will change to white if they feel like it could get too rough.Black voodoo is a dmg mode,and it hurts like hell. Psy loses a lot of def,and they are super squishy now. Watch on your hp however,it can go down rly fast.Psychic will,immune to phy dmg that psys use,it lasts 8/10 sec and it has 30 sec cd. No point in hitting a psy when he uses it,better change to true form and tank.Watch on SoS,its a purple-blue barrier around a psy that will stun you for 11-12 sec,can be countered with antistun.As of silence,its a self buff,and cd is same as duration,so psy will just rebuff when it ends. It has a chance to silence you for 3sec,you can counter it will genie skill will surge or belif.EDIT: psys use water and earth skills, keep an eye on tide spirit,it removes chan and increases dmg for a short period,its when psy goes for the kill.