Insight

Whenever an opponent casts a green spell, you draw a card.

Homarid Shaman

Hydroblast

Choose one —
• Counter target spell if it's red.
• Destroy target permanent if it's red.

Tidal Visionary

{T}: Target creature becomes the color of your choice until end of turn.

Llawan, Cephalid Empress

When Llawan, Cephalid Empress enters, return all blue creatures your opponents control to their owners' hands.
Your opponents can't cast blue creature spells.

Sway of Illusion

Any number of target creatures become the color of your choice until end of turn.
Draw a card.

Shifting Sky

As Shifting Sky enters, choose a color.
All nonland permanents are the chosen color.

Tidebinder Mage

When Tidebinder Mage enters, tap target red or green creature an opponent controls. That creature doesn't untap during its controller's untap step for as long as you control Tidebinder Mage.

Vodalian Mystic

{T}: Target instant or sorcery spell becomes the color of your choice.

Scuttlemutt

{T}: Add one mana of any color.
{T}: Target creature becomes the color or colors of your choice until end of turn.

Aether Gust

Choose target spell or permanent that's red or green. Its owner puts it on their choice of the top or bottom of their library.

Flash Flood

Choose one —
• Destroy target red permanent.
• Return target Mountain to its owner's hand.

Douse

Blind Seer

{1}{U}: Target spell or permanent becomes the color of your choice until end of turn.

Painter's Servant

As Painter's Servant enters, choose a color.
All cards that aren't on the battlefield, spells, and permanents are the chosen color in addition to their other colors.

Well-Laid Plans

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

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Cowardice

Whenever a creature becomes the target of a spell or ability, return that creature to its owner's hand. (It won't be affected by the spell or ability.)

Willbreaker

Whenever a creature an opponent controls becomes the target of a spell or ability you control, gain control of that creature for as long as you control Willbreaker.

Wash Out

Return all permanents of the color of your choice to their owners' hands.

Dismiss into Dream

Each creature your opponents control is an Illusion in addition to its other types and has "When this creature becomes the target of a spell or ability, sacrifice it."

Distorting Lens

{T}: Target permanent becomes the color of your choice until end of turn.

Wrath of Marit Lage

When Wrath of Marit Lage enters, tap all red creatures.
Red creatures don't untap during their controllers' untap steps.