Feedback Elemental

Creature - Mutant
Flash
As you play Feedback Elemental, choose an opponent. Feedback Elemental costs

less for each mana in that opponent's mana pool.
At the begining of each players upkeep, for each different color mana you have in your mana pool, Feedback Elemental gains Protection from that color until end of turn.
7/7
The final (for now) installment of cards that mess with your opponent in reguards to thier mana pool. This one is really the coup-de-gras of cards of this nature. A real powerhouse, evassion creature, that gets easier to cast based on the ammount of mana your opponent is stashing.
Outside of Type 1, this guy is actually fairly janky... If your opponent plays tight then there will be very few oppertunities to play this guy for any less than 7-9 mana. In context of type 1, cards like mana drain or tolarian academy can be hard to spend all at once, so this probably grows in powerlevel there.
"All right! enough of this! Prismatic Arc should be Red, Essential Balance should be Red, and Feedback Elemental should be White! Stop screwing with the pie!!"
I think of "floating Mana" as some sort of excess energy in the atmosphere. It seems like Red could really care less about harnessing excess mana. If anything its more chaotic and caustic of the excess.
In that context, I think Essential Balance is good in green, becasue green would seek to equalize and generate its own engergy when confronting this excess.
Prismatic Arc is an arc of energy that is powerful when left along, but is weak enough to become fragmented and disapated when confronted by this energy.
And a crafty wizard could easily use a differential in energy to summon monsterous elemental of pure energy.
In the basic concept of the cards, White-Damage, Green-mana production, Blue-large creature with protection .... This mechanic I think is inharently very weak. It really relies on your opponent playing right into your cards. Putting these cards into thier appropriate color would make them #1 weak by comparison, #2 out of flavor IMO.