From WoWWiki

Bonuses for Dodge can only be obtained through Red Gems, Orange Gems and Purple Gems.

Color	Name	Effect(s)
Red	[Subtle Living Ruby]	+8 Dodge
	[Subtle Crimson Spinel]	+10 Dodge
Orange	[Beaming Fire Opal]	+5 Dodge	+4 Resilience
	[Nimble Fire Opal]	+5 Dodge	+4 Melee Hit
	[Stalwart Fire Opal]	+4 Dodge	+5 Defense
	[Assassin's Fire Opal]	+5 Dodge	+6 Melee Critical
Purple	[Regal Tanzanite]	+5 Dodge	+6 Stamina