This happens while leveling the mob con color does not update unless you zone or relog your character.
Before leveling

After Leveling

After Reloging

Since this is about con coloring, I'll post it here.
I just spawned The Sinking Sands, and noticed that all the NPCs are "grey" even though I am level 1, and they are levels 49-52 etc. Using /spawn set level # to change his level to 1 does not turn him from gray to white (which might be chrrox' issue).
If I leave the npc at level 1 and restart the zone, the proper color appears. So the dynamic changing is a bug, and also NPCs above a certain level are not conned properly (?)

I've also seen this problem before. Even if you stand in front of a NPC and type /level 100, the con colour still does not change.