There are 4 different colors of gear,

Pink- Atherial Gear- Pink Gear is pieces of common usually craftable gear that have random augmented stats attached to them. These are by no means special most of the time, but every now and again you can come across a special gem that has some really good bonus augments attached.

Green- Scarace Gear- Green Gear is special gear that has a higher than average stats and item levels compared to gear of the same equippable level. You can kind of think of these pieces of gear as a HQ +2, but they are not by any means leaps and bounds better than normal gear for their level.

Blue- Rare Gear (Not to be confused with R/EX)- Blue gear is special gear and usually has a much higher stats over Scarace Gear. This type of gear's item level also varies greatly, and typically you won't see any Blue gear that has an item level below 50.