The intention was to give each color a set of main effects, as well as some variety of removal and some variety of reanimator package.
White:
• Bears/Protection/Tap "Fairness" Effects
• Blink Effects
• Alt-Win-Con
Blue:
• Mill
• Flashback
• Control
Black:
• Discard
• Midrange Modular Creatures
• Extra Reanimator
Red:
• Repeatable Burn
• Wide Tokens
• Mana Generation
Green:
• Aggro Creatures
• Permeating-Mass copy effects
• Midrange Tokens