I’ll have a shot at this!
Green: Board control by big numbers and economical advantages
Growth: Buffing
Feral: Big bodies with strong keywords
Balance: Reactive; has a theoretical answer to most pure strategies
Red: Aggro
Anarchy: Haste
Blood: Swarming, suicide
Fire: Non-combat damage
White: Strong heroes with robust and flexible units
Discipline: cards that buff and protect each other
Ninjutsu: Avoiding trades with swift strike, deathtouch or by ignoring patrollers
Strength: High defense, supported by cheap early flyers
Blue: Control
Truth: Illusions and copies
Peace: Straight-forward combat; card advantage
Law: Control via disables, removal and restricting enemy options
Black: Forced discard, sacrifices, very specc-specific strategies/gimmicks
Demonology: Strong cards with unique drawbacks
Necromancy: Removal and tokens
Disease: - 1/-1 runes
Purple: Time runes, bouncing, mid-late game
Past: Fading, bouncing (returning cards to hand)
Present: Haste, readying, summoning units from your Codex
Future: Foresight, powerful flyers
Finesse: Agression, combos
Bashing: flexible combination of slightly weaker versions of other speccs’ cards