Glad to hear...now let's see if it holds true!

MULTI
White and blue seem to end up with the best cards here.

Commons
1) Messenger Hawk
2) Abandon Attachments
3) Vindictive Warden

Uncommons
1) Jet, Freedom Fighter
2) Hama, the Bloodbender

Rare
1) Katara, Water Tribe's Hope

GREEN
Best at splashing, self mill and ramp. Commons aren't that impressive so probably relies more on higher rarity cards

Commons
1) Rocky Rebuke
2) Ostrich-Horse
3) Raucous Audience

Uncommons
1) Toph, the Blind Bandit
2) Unlucky Cabbage Merchant

Rare
1) The Earth King

RED
Main colour that's very strong at common. Best at aggression, with top removal spells and very few bad cards. Can be built easily at low rarity

Commons
1) Firebending Lesson
2) Lightning Strike
3) Fire Nation Cadets

Uncommons
1) Fire Nation Attacks
2) Iroh's Demonstration

Rare
1) Ran and Shaw

BLACK
Narrow roster of good commons with good cheap cards that generate value. Best as a support colour in a sacrifice space

Commons
1) Callous Inspector
2) Corrupt Court Official
3) Sold Out
4) Merchant of Many Hats

Uncommons
1) Heartless Act
2) June, Bounty Hunter

Rare
1) The Fire Nation Drill

BLUE
Best late-game colour but with tools to play a tempo game. Somewhat hurt by the lack of a hard counter at common.

Commons
1) Forecasting Fortune Teller
2) Lost Days
3) Watery Grasp

Uncommons
1) Katara, Bending Prodigy
2) Accumulate Wisdom

Rare
1) The Mechanist

WHITE
Very flexible as either support or main colour. Fairly deep roster of commons and lots of strong uncommons. Tools for both aggro and control.

Commons
1) Kyoshi Warriors
2) Airbending Lesson
3) Glider Kids

Uncommons
1) Water Tribe Rallier
2) Team Avatar

Rare
1) Avatar's Wrath

I forgot to say but when playing against David Mines I somehow soul read his last card in hand with The Rise of Sozin which felt insanely lucky.