Roxanne, Starfall Savant

Whenever Roxanne enters or attacks, create a tapped colorless artifact token named Meteorite with "When this token enters, it deals 2 damage to any target" and "{T}: Add one mana of any color."
Whenever you tap an artifact token for mana, add one mana of any type that artifact token produced.

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Sol Ring

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.