Based on the latest market prices tracked on TCG Stacked, Psychotic Haze is worth about $0.21 USD for a regular copy and $2.10 USD for a foil copy
A few different cards fall under this definition, including anthems, mass pump spells, auras, combat tricks, and cards that dispense +1/+1 counters
I would make it a flyer and give it haste, maybe even double strike
Essentially, if you have a full party with all four of these on the board, you can pay one white, one blue, and one black mana to give the Warrior lifelink, deathtouch, and make him unblockable (deathtouch and unblockable at the same time has no real use, but thats still OP to think about)
Incapsula incident ID: 1553000690298233402-557057795263893839
While the deckbuilding restriction wont let you put every multicolored card you might want into your deck, Magics card pool is large enough to make it trivial