Can a commander with a color identity of blue and green use a land that produces white mana?

In Commander, every card in your deck must have a color identity that is a subset of your commander's color identity (CR 903.5b). Color identity is not just about a card's mana cost — it includes any mana symbols appearing anywhere in the card's rules text as well (CR 903.4).

A land that produces white mana (for example, a basic Plains, or a card with '{T}: Add {W}' in its text) has white ({W}) in its color identity. Since white is not part of a blue/green commander's color identity, such a land is illegal in that deck.

There is an important exception: basic land types (Plains, Island, Swamp, Mountain, Forest) on a land do not by themselves determine color identity — it's the mana symbols in the rules text that matter. A card like 'Azorius Guildgate' has {W} and {U} symbols in its text, giving it a white and blue identity, which would also be illegal in a blue/green deck.

Concrete example: Suppose your commander is Momir Vig, Simic Visionary (green/blue identity). You cannot include a Hallowed Fountain (which produces {W} and {U}) because its text contains {W}, adding white to its color identity — a color outside your commander's identity.

Lands that only produce {G}, {U}, or colorless mana (like Simic Growth Chamber or Wastes) are perfectly legal. Always check every mana symbol in a card's text when evaluating color identity (CR 903.4).