Plains

Avacyn's Pilgrim

Fyndhorn Elves

Ornithopter of Paradise

Poison Dart Frog

Reach
{T}: Add one mana of any color.
{2}: Poison Dart Frog gains deathtouch until end of turn.

Sanctum Weaver

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

Forest

Leafkin Druid

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

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.

Llanowar Elves

Elvish Mystic

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.

Lotus Cobra

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

Copper Myr

Gold Myr

Paradise Druid

Paradise Druid 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.

Manakin

Hedron Crawler

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

Devoted Druid

{T}: Add {G}.
Put a -1/-1 counter on Devoted Druid: Untap Devoted Druid.

Vine Trellis

Defender (This creature can't attack.)
{T}: Add {G}.

Magus of the Vineyard

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

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.

Tangled Vale

Tangled Vale enters tapped.
{T}: Add {G}.

Tangled Florahedron

Tangled Florahedron // Tangled Vale

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}."