Govern the Guildless

Gain control of target monocolored creature.
Forecast — {1}{U}, Reveal Govern the Guildless from your hand: Target creature becomes the color or colors of your choice until end of turn. (Activate only during your upkeep and only once each turn.)

Change the Equation

Choose one —
• Counter target spell with mana value 2 or less.
• Counter target red or green spell with mana value 6 or less.

Dromar, the Banisher

Flying
Whenever Dromar, the Banisher deals combat damage to a player, you may pay {2}{U}. If you do, choose a color, then return all creatures of that color to their owners' hands.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Dream Coat

Enchant creature
{0}: Enchanted creature becomes the color or colors of your choice. Activate only once each turn.

Vodalian Mystic

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

Sol Ring

Trait Doctoring

Change the text of target permanent by replacing all instances of one color word with another or one basic land type with another until end of turn.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Tidal Visionary

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

Sleight of Mind

Change the text of target spell or permanent by replacing all instances of one color word with another. (For example, you may change "target black spell" to "target blue spell." This effect lasts indefinitely.)

Blind Seer

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

Flooded Woodlands

Green creatures can't attack unless their controller sacrifices a land for each green creature they control that's attacking. (This cost is paid as attackers are declared.)

Shifting Sky

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

Order of the Sacred Torch

{T}, Pay 1 life: Counter target black spell.

Warped Devotion

Whenever a permanent is returned to a player's hand, that player discards a card.

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Wash Out

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

Solemn Simulacrum

When Solemn Simulacrum enters the battlefield, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When Solemn Simulacrum dies, you may draw a card.

Orzhov Signet

Sway of Illusion

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

Llawan, Cephalid Empress

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

Ersatz Gnomes

{T}: Target spell becomes colorless.
{T}: Target permanent becomes colorless until end of turn.

Perish

Destroy all green creatures. They can't be regenerated.

Island

Swamp

Arcane Signet

Scuttlemutt

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

Eight-and-a-Half-Tails

{1}{W}: Target permanent you control gains protection from white until end of turn.
{1}: Target spell or permanent becomes white until end of turn.

Robe of Stars

Equipped creature gets +0/+3.
Astral Projection — {1}{W}: Equipped creature phases out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)
Equip {1}

Distorting Lens

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

Hibernation

Return all green permanents to their owners' hands.

Deathgrip

Douse

Alter Reality

Change the text of target spell or permanent by replacing all instances of one color word with another. (This effect lasts indefinitely.)
Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)