Voici les questions et les réponses depuis la rubrique Cranial Insertion de MTGSalvation (donc autant vous dire que vous allez pas les contredire)
Q: If I happen to have a Reflecting Pool in play and my only other land is a River of Tears, and I have not played a land this turn, can I tap the Pool to get

? What about getting

out of it once I've laid a land, since this is what the River usually produces?
A: In this case, Reflecting Pool behaves exactly as River of Tears would. If will tap for

if you haven’t played a land yet this turn, and for

if you have. River of Tears has a self-replacement effect, and Reflecting Pool applies that when it determines which color(s) the River “could produce.”
Q: What about Reflecting Pool and a Vivid Land with no counters on it? Can I still tap the Pool for one mana of any color?
A: You can. The fact that you can't actually pay the cost of the Vivid land's any-color ability (removing a counter) doesn't matter.
What DOES matter when you're evaluating what Reflecting Pool can and can't do? This metric went out on the MTGRULES-L list, posted by the Netrep there, Gavin Duggan,so it's [O]fficial.
* It DOES take into account replacement effects (Reality Twist) and self-replacement effects (River of Tears)
* It does NOT take into account costs on the mana ability in question (Crystal Quarry,%t , etc)
* It does NOT take into account play restrictions (Tainted Peak, Temple of the False God)
* It does NOT take into account other possible futures (Playing a land, a Blood Moon, or a Stone Rain)