Stat budget differs between each piece of gear. If you're trying to meld a stat and it shows up in red, it means doing so will cap out the stat or it already is capped.

For an idea what is on and the CP caps are for each ilvl 690 item:

Main Hand: 0/8
Off Hand: 0/8
Head: 10/11
Body: 6/8
Hands: 10/11
Legs: 0/11
Feet: 0/11
Earring: 81/95
Necklace: 81/95
Bracelet: 81/95
Ring: 42/49

This means melding CP in your Earring, Necklace, Bracelet, then followed by Legs and Feet will give you the most benefit.