Magus of the Vineyard

At the beginning of each player's first main phase, that player adds {G}{G}.

Gold Myr

Fyndhorn Elves

Sanctum Weaver

{T}: Add X mana of any one color, where X is the number of enchantments you control.

Karametra, God of Harvests

Indestructible
As long as your devotion to green and white is less than seven, Karametra isn't a creature.
Whenever you cast a creature spell, you may search your library for a Forest or Plains card, put it onto the battlefield tapped, then shuffle.

Joraga Treespeaker

Level up {1}{G} ({1}{G}: Put a level counter on this. Level up only as a sorcery.)
LEVEL 1-4
1/2
{T}: Add {G}{G}.
LEVEL 5+
1/4
Elves you control have "{T}: Add {G}{G}."

Ornithopter of Paradise

Devoted Druid

{T}: Add {G}.
Put a -1/-1 counter on this creature: Untap this creature.

Avacyn's Pilgrim

Hedron Crawler

{T}: Add {C}. ({C} represents colorless mana.)

Lotus Cobra

Landfall — Whenever a land you control enters, add one mana of any color.

Poison Dart Frog

Reach
{T}: Add one mana of any color.
{2}: This creature gains deathtouch until end of turn.

Plains

Forest

Llanowar Elves

Tangled Vale

Tangled Florahedron

Tangled Florahedron // Tangled Vale

Katilda, Dawnhart Prime

Protection from Werewolves
Human creatures you control have "{T}: Add one mana of any of this creature's colors."
{4}{G}{W}, {T}: Put a +1/+1 counter on each creature you control.

Leafkin Druid

{T}: Add {G}. If you control four or more creatures, add {G}{G} instead.

Elvish Mystic

Ilysian Caryatid

{T}: Add one mana of any color. If you control a creature with power 4 or greater, add two mana of any one color instead.

Manakin

Copper Myr

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.