On the Question of "Any color" lands and Colorless generals that came up at prerelease today
Looking more into it
Comprehensive rule 903.9
903.9. If mana would be added to a player’s mana pool of a color that isn’t in the color identity of that player’s commander, that amount of colorless mana is added to that player’s mana pool instead.
Comprehensive Rule 106.4
106.4. When an effect produces mana, that mana goes into a player’s mana pool. From there, it can be used to pay costs immediately, or it can stay in the player’s mana pool. Each player’s mana pool empties at the end of each step and phase.
From the MTGCommander.net EDH FAQ post by Ban Ki Moon of the Rules Commity
What if I have a reflecting Pool or a 5 color mana producer
Reflecting Pool, Darksteel Ingot and cards like them can be played in any Commander deck, since they have no mana symbols on them to make them illegal. You can choose to make any color of mana that they could produce, but if you choose a color outside of your color identity you get colorless instead. Basically, any time colored mana would be added to your mana pool, it turns colorless if it doesn't match your commander.
From another MTG Commander Thread that has had input from members of the rules commity
List of Colorless lands
See also Rule 605 (Mana Abilities)
Nothing about rule 903.9 Modifies which mana abilities can be activated by a player nor does 903.4 Color Identy
Nothing in rule 605 States anything about limiting which mana abilities a player may choose to activate
Mana abilities (605) Cause Mana to be produced
605.1a An activated ability is a mana ability if it meets three criteria: it doesn’t have a target, it could put mana into a player’s mana pool when it resolves, and it’s not a loyalty ability. (See rule 606, “Loyalty Abilities.”)
605.1b A triggered ability without a target that triggers from activating a mana ability and could put mana into a player’s mana pool when it resolves is a mana ability.
605.3 Defines when mana abilities can be activated but does not limit which ones can be activated
605.3. Activating an activated mana ability follows the rules for activating any other activated ability (see rule 602.2), with the following exceptions:
605.3a A player may activate an activated mana ability whenever he or she has priority, whenever he or she is casting a spell or activating an ability that requires a mana payment, or whenever a rule or effect asks for a mana payment, even if it’s in the middle of casting or resolving a spell or activating or resolving an ability.
605.3b An activated mana ability doesn’t go on the stack, so it can’t be targeted, countered, or otherwise responded to. Rather, it resolves immediately after it is activated. (See rule 405.6c.)
Activating an ability which meats the criteria for being a Mana abiliity per 605.1a
Causes mana to be added to your mana pool (See 106.4 above)
If A player chooses per 605.3 to activate a mana ability and they have priority they add mana to their pool per 106.4 which in a commander game is modified 903.9 such that the following check is performed
If Mana being added to pool is in Color Identity Add to pool else replace with colorless
So from everything I can Glean from MTGcommander.net foum postings, and the comprehensive rules the person who was claiming MODO alows him to use City Of Brass in a colorless EDH deck was indeed correct by the rules.
CoB has no Color Identity, Nothing in any portion of the comprehensive rules, or rule 4 of the Commander rules (which maps to comp rule 903.9) limits the choosing to produce an outside color identity mana nor the activation of the mana ability that could possibly generate it.
A colorless generals color identity is colorless, I the controller of that general am not limited in any way in the choices I can make when activating my mana abilities pending those abilities are on cards which meet the deck construction guidelines and match my color identity (Which City of Brass et al do)