Vibrant Outburst

Three damage to any target is the number Izzet has priced its removal against since red burn first existed, so what earns the second color here is the clause bolted underneath it: tapping up to one creature turns a kill spell into a partial Fog stapled to a Bolt. Point the damage at whatever needs to die, then reach across the board to pin down an attacker or blocker the burn never touched. The tap is optional and fully independent (the "up to one" phrasing lets you decline it entirely, or tap a creature while the three goes at a planeswalker or the opponent's face), which means one card resolves as either a combat two-for-one or a tempo tax that buys a turn. Mono-red gets the burn but never the tap; mono-blue can tap all day but cannot deal three. This lives exactly on the seam between them, doing the aggressive thing and the controlling thing in a single instant-speed window. It descends from the long Izzet tradition of spells that do two jobs at once, and it justifies that lineage by keeping the two halves genuinely separable rather than welding the disruption to the removal.