Treva, the Renewer

Flying
Whenever Treva deals combat damage to a player, you may pay {2}{W}. If you do, choose a color, then you gain 1 life for each permanent of that color.

Brine Seer

{2}{U}, {T}: Reveal any number of blue cards in your hand. Counter target spell unless its controller pays {1} for each card revealed this way.

Painter's Servant

As this creature 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.

Shifting Sky

As this enchantment enters, choose a color.
All nonland permanents are the chosen color.

Aven Warcraft

Creatures you control get +0/+2 until end of turn.
Threshold — If there are seven or more cards in your graveyard, choose a color. Creatures you control also gain protection from the chosen color until end of turn.

Bathe in Light

Radiance — Choose a color. Target creature and each other creature that shares a color with it gain protection from the chosen color until end of turn.

Chameleon Spirit

As this creature 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.

Benevolent Blessing

Flash
Enchant creature
As this Aura enters, choose a color.
Enchanted creature has protection from the chosen color. This effect doesn't remove Auras and Equipment you control that are already attached to it.