Emyehem, Prismatic Convergence

Emyehem, Prismatic Convergence is all colors.
Whenever you cast a spell, choose a color not in that spell's colors. That spell becomes that color in addition to its other colors. If you chose— white: Emyehem gains protection from the color of your choice until end of turn; blue: return target permanent to its owner's hand; black: target opponent exiles a card from their hand; red: Emyehem deals 4 damage to any tar