These are the current colours from the PTR, taken from the epic gem recipes you can purchase.
Red: Intellect, Strength, Agility, Expertise, Parry.
Blue: Stamina, Spirit, Spell Penetration, Hit.
Yellow: Dodge, Crit, Resilliance, Haste.
The changed once are:
Intellect, yellow->red.(well, this is basicly just the spellpower gem now)
All mixed gems are obviously changed accordingly. This might change ofcourse, and i might have missed something aswell, but this is how it is right now atleast.