What's the Gear Quality Coloring system here?

just finished up my first dungeon, and I got a Pink-quality weapon out of the run...

Pink?

what happened to White->Green->Blue->Purple->Yellow?

what's the color system in this game?

Gear color progression

Pink and Green are actually considered same level.

Green gear will have set stats on it, so everyone who gets that piece of gear will have the stats same.

Pink, while the gear level is considered the same as green, it's stats still vary, so 2 people can actually wear the same pink piece but have different stats.

Pink stays in the lower end dungeons though, I am not aware of any pink gear past level 40 though.

My ring is level 47 and pink! http://xivdb.com/?item/4515/Aetherial-Black-Pearl-Ring

It does seem like pink becomes rarer though, after 40. Instances tend to favor green at this point, I think.

Pink gear is a variant on white gear that has random bonus stats, while green and blue gear has set stats. There doesn't really seem to be a notable difference between green and blue gear in terms of performance, but what few differences are as follows:

All unique dungeon drops are green.
All level 90 accessories (bought with mythology tomestones) are green.
All items crafted with dungeon dropped materials, or level 50+ crafted items, are green.
All artifact armor is blue.
All darklight armor is blue.
All primal weapons are blue
Green (and pink) items can be turned in to your grand company for seals, and can be converted.
Blue items cannot be removed.
I've probably missed a few.

As a general rule...

White -> Pink -> Green -> Blue -> Purple