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.

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Tidal Visionary

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

Sway of Illusion

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

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.

Sol Ring

Arcane Signet

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

Wash Out

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

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.)

Dream Coat

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

Distorting Lens

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

Shifting Sky

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

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.

Whim of Volrath

Buyback {2} (You may pay an additional {2} as you cast this spell. If you do, put this card into your hand as it resolves.)
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. (For example, you may change "nonred creature" to "nongreen creature" or "plainswalk" to "swampwalk.")