Douse

Vodalian Mystic

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

Escape Routes

{2}{U}: Return target white or black creature you control to its owner's hand.

Tidal Visionary

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

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Sway of Illusion

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

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.

Fylamarid

Flying
Fylamarid can't be blocked by blue creatures.
{U}: Target creature becomes blue until end of turn.

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.)

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.

Blind Seer

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

Distorting Lens

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

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.

Shifting Sky

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

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.

King Crab

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

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.

Omen Hawker

{T}: Add {C}{U}. Spend this mana only to activate abilities.

Insight

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

Chameleon Spirit

As Chameleon Spirit enters, choose a color.
Chameleon Spirit's power and toughness are each equal to the number of permanents of the chosen color your opponents control.

Flash Flood

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