Wrath of Marit Lage

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

Vodalian Mystic

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

Prismwake Merrow

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

Weatherseed Faeries

Shifting Sky

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

Douse

Coast Watcher

Archaeomancer

When Archaeomancer enters, return target instant or sorcery card from your graveyard to your hand.

Snap

Return target creature to its owner's hand. Untap up to two lands.

Cerulean Drake

Flying
Protection from red (This creature can't be blocked, targeted, dealt damage, enchanted, or equipped by anything red.)
Sacrifice Cerulean Drake: Counter target spell that targets you.

Sea Sprite

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Crypsis

Target creature you control gains protection from creatures your opponents control until end of turn. Untap it.

Prismatic Lace

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

Hydroblast

Choose one —
• Counter target spell if it's red.
• Destroy target permanent if it's red.

Scuttlemutt

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

Tidal Visionary

{T}: Target creature 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.

Sway of Illusion

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

Hibernation

Return all green permanents to their owners' hands.

Blind Seer

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

Essence Leak

Enchant permanent
As long as enchanted permanent is red or green, it has "At the beginning of your upkeep, sacrifice this permanent unless you pay its mana cost."

Wash Out

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

Flash Flood

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

Well-Laid Plans

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