Common Cause

Nonartifact creatures get +2/+2 as long as they all share a color.

Jaded Response

Counter target spell if it shares a color with a creature you control.

Well-Laid Plans

Prevent all damage that would be dealt to a creature by another creature if they share a color.

Tsabo's Assassin

{T}: Destroy target creature if it shares a color with the most common color among all permanents or a color tied for most common. A creature destroyed this way can't be regenerated.

Brightflame

Radiance — Brightflame deals X damage to target creature and each other creature that shares a color with it. You gain life equal to the damage dealt this way.

Ana Sanctuary

At the beginning of your upkeep, if you control a blue or black permanent, target creature gets +1/+1 until end of turn. If you control a blue permanent and a black permanent, that creature gets +5/+5 until end of turn instead.

Crown of Convergence

Play with the top card of your library revealed.
As long as the top card of your library is a creature card, creatures you control that share a color with that card get +1/+1.
{G}{W}: Put the top card of your library on the bottom of your library.

Spreading Plague

Whenever a creature enters the battlefield, destroy all other creatures that share a color with it. They can't be regenerated.

Wojek Siren

Radiance — Target creature and each other creature that shares a color with it get +1/+1 until end of turn.