Flash Flood

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

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.

Inundate

Return all nonblue creatures to their owners' hands.

Wrath of Marit Lage

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

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.

King Crab

{1}{U}, {T}: Put target green creature on top of its owner's library.

Hibernation

Return all green permanents 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."

Scuttlemutt

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

Distorting Lens

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

Training Grounds

Activated abilities of creatures you control cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Douse

Well-Laid Plans

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

Glamerdye

Change the text of target spell or permanent by replacing all instances of one color word with another.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Shifting Sky

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

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.

Insight

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

Homarid Shaman

Blind Seer

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