Historical Rules · 23 April 2010
Rule 903.4d
Official source text from the 23 April 2010 Rules release
A basic land card may be included in an EDH deck only if it could produce a color of mana that's in the general's mana cost. Example: A deck has a white-blue general. It may include basic Plains and basic Islands, but not basic Swamps, basic Mountains, or basic Forests.