Windborn Muse

Flying
Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Rainbow Crow

Flying
{1}: Rainbow Crow becomes the color of your choice until end of turn.

Infuse with the Elements

Converge — Put X +1/+1 counters on target creature, where X is the number of colors of mana spent to cast this spell. That creature gains trample until end of turn.

Reality

Illusion

Target spell or permanent becomes the color of your choice until end of turn.

Illusion // Reality

Selfless Spirit

Flying
Sacrifice Selfless Spirit: Creatures you control gain indestructible until end of turn.

Chulane, Teller of Tales

Vigilance
Whenever you cast a creature spell, draw a card, then you may put a land card from your hand onto the battlefield.
{3}, {T}: Return target creature you control to its owner's hand.

Unsettled Mariner

Changeling (This card is every creature type.)
Whenever you or a permanent you control becomes the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays {1}.

Knight of New Alara

Each other multicolored creature you control gets +1/+1 for each of its colors.

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.)

Tidal Visionary

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

Grand Arbiter Augustin IV

White spells you cast cost {1} less to cast.
Blue spells you cast cost {1} less to cast.
Spells your opponents cast cost {1} more to cast.

Quickchange

Target creature becomes the color or colors of your choice until end of turn.
Draw a card.

Faeburrow Elder

Vigilance
Faeburrow Elder gets +1/+1 for each color among permanents you control.
{T}: For each color among permanents you control, add one mana of that color.

Sway of Illusion

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

Scuttlemutt

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

Swirling Spriggan

{G/U}{G/U}: Target creature you control becomes the color or colors of your choice until end of turn.

Paradise Druid

This creature has hexproof as long as it's untapped. (It can't be the target of spells or abilities your opponents control.)
{T}: Add one mana of any color.

Mechtitan Core

{5}, Exile Mechtitan Core and four other artifact creatures and/or Vehicles you control: Create Mechtitan, a legendary 10/10 Construct artifact creature token with flying, vigilance, trample, lifelink, and haste that's all colors. When that token leaves the battlefield, return all cards exiled with Mechtitan Core except Mechtitan Core to the battlefield tapped under their owners' control.
Crew 2

Iridian Maelstrom

Destroy each creature that isn't all colors.

Prismatic Lace

Target permanent becomes the color or colors of your choice. (This effect lasts indefinitely.)

Blind Seer

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

Common Cause

Nonartifact creatures get +2/+2 as long as they all share a color.

Transguild Courier

Scrapbasket

{1}: Scrapbasket becomes all colors until end of turn.

Kavu Chameleon

This spell can't be countered.
{G}: Kavu Chameleon becomes the color of your choice until end of turn.

Birds of Paradise

Brilliant Spectrum

Converge — Draw X cards, where X is the number of colors of mana spent to cast this spell. Then discard two cards.

Sphinx of the Guildpact

Sphinx of the Guildpact is all colors.
Flying
Hexproof from monocolored (This creature can't be the target of monocolored spells or abilities your opponents control.)

Chromatic Orrery

You may spend mana as though it were mana of any color.
{T}: Add {C}{C}{C}{C}{C}.
{5}, {T}: Draw a card for each color among permanents you control.

Noble Hierarch

Exalted (Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn.)
{T}: Add {G}, {W}, or {U}.

Planewide Celebration

Choose four. You may choose the same mode more than once.
• Create a 2/2 Citizen creature token that's all colors.
• Return target permanent card from your graveyard to your hand.
• Proliferate.
• You gain 4 life.

Shyft

At the beginning of your upkeep, you may have Shyft become the color or colors of your choice. (This effect lasts indefinitely.)

Elesh Norn, Grand Cenobite

Vigilance
Other creatures you control get +2/+2.
Creatures your opponents control get -2/-2.

Wild Mongrel

Discard a card: Wild Mongrel gets +1/+1 and becomes the color of your choice until end of turn.

Bloom Tender

{T}: For each color among permanents you control, add one mana of that color.

Soul of Ravnica

Flying
{5}{U}{U}: Draw a card for each color among permanents you control.
{5}{U}{U}, Exile Soul of Ravnica from your graveyard: Draw a card for each color among permanents you control.

Fallaji Wayfarer

Fallaji Wayfarer is all colors. This ability doesn't affect its color identity. (It can be in any deck whose commander's color identity includes green.)
Multicolored spells you cast have convoke. (Your creatures can help cast those spells. Each creature you tap while casting a multicolored spell pays for {1} or one mana of a color that creature is.)

Prismwake Merrow

Flash
When Prismwake Merrow enters, target permanent becomes the color or colors of your choice until end of turn.

Conqueror's Flail

Equipped creature gets +1/+1 for each color among permanents you control.
As long as Conqueror's Flail is attached to a creature, your opponents can't cast spells during your turn.
Equip {2}

Sisay's Ingenuity

Enchant creature
When Sisay's Ingenuity enters, draw a card.
Enchanted creature has "{2}{U}: Target creature becomes the color of your choice until end of turn."