Rule 903.5c

A card can't be included in a Commander deck if it has any colors that aren't part of the commander's color identity or if it has any mana symbols in its mana cost or rules text that aren't of a color in the commander's color identity. Example: Wort, the Raidmother is a legendary creature with mana cost {4}{(R/G){R/G}. Wort's color identity is red and green. Each card in a Wort Commander deck must be only red, only green, both red and green, or have no color. Each mana symbol in the mana cost or rules text of a card in this deck must be only red, only green, both red and green, or have no color.

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