This question already has an answer here:
A couple of other questions have been asked regarding cards that "Add one mana of any color to your mana pool", but
- One is for EDH decks in general (which, in most cases, have at least one color)
- The other is for colorless mana in general (which would likely also be used in a colored deck, or a non-EDH deck where extra colors don't matter)
What I'm trying to answer now is if those sorts of cards can be used in a colorless EDH deck.
So, for example, if I have one of the big Eldrazi as my commander, I know I can have Coalition Relic in the deck because it has a colorless color identity. But, once it's on the field, can I use it to generate usable mana?