Font Color of Player Names

hey all, i have a question about the light blue/dark blue font color of player names. why is it done that way? at first i thought it had to do with being in a party, but noticed when i invited people to my party that some that were dark blue or light blue were not in a party. thanks in advance.

Light Blue - Not in a Party
Dark Blue - In a Party

Sometimes the game doesn't register right away if a player joined/left a party.

Also - to be more technical, when you click a person's name who was in a party, their name will be dark blue like normal. BUT, when they leave the party their name will still be dark blue (only to you) until you move your mouse cursor over it (and it will turn back to light blue). It's kind of like cache refreshing; sort of. The opposite of this scenario is also true for transitioning from light blue to dark blue if they join a group and if you had their name selected.