Bloom Tender

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

Jared Carthalion

+1: Create a 3/3 Kavu creature token with trample that's all colors.
−3: Choose up to two target creatures. For each of them, put a number of +1/+1 counters on it equal to the number of colors it is.
−6: Return target multicolored card from your graveyard to your hand. If that card was all colors, draw a card and create two Treasure tokens.
Jared Carthalion can be your commander.

Prismabasher

Trample
Vivid — When this creature enters, up to X target creatures you control get +X/+X until end of turn, where X is the number of colors among permanents you control.

Shimmercreep

Menace (This creature can't be blocked except by two or more creatures.)
Vivid — When this creature enters, each opponent loses X life and you gain X life, where X is the number of colors among permanents you control.

Sanar, Innovative First-Year

Vivid — At the beginning of your first main phase, reveal cards from the top of your library until you reveal X nonland cards, where X is the number of colors among permanents you control. For each of those colors, you may exile a card of that color from among the revealed cards. Then shuffle. You may cast the exiled cards this turn.

Leyline of the Guildpact

If this card is in your opening hand, you may begin the game with it on the battlefield.
Each nonland permanent you control is all colors.
Lands you control are every basic land type in addition to their other types.

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.)

Faeburrow Elder

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

Luminollusk

Deathtouch
Vivid — When this creature enters, you gain life equal to the number of colors among permanents you control.

Shinestriker

Flying
Vivid — When this creature enters, draw cards equal to the number of colors among permanents you control.

Aurora Awakener

Trample
Vivid — When this creature enters, reveal cards from the top of your library until you reveal X permanent cards, where X is the number of colors among permanents you control. Put any number of those permanent cards onto the battlefield, then put the rest of the revealed cards on the bottom of your library in a random order.

Prismatic Undercurrents

Vivid — When this enchantment enters, search your library for up to X basic land cards, where X is the number of colors among permanents you control. Reveal those cards, put them into your hand, then shuffle.
You may play an additional land on each of your turns.

Explosive Prodigy

Vivid — When this creature enters, it deals X damage to target creature an opponent controls, where X is the number of colors among permanents you control.