In the Dresden Files, we have seen what is considered formal attire in the White Council meetings.
Per the wiki:
Formal robes were flowing black with stoles of satin and silk in one of the various colors and pattern of trim that denoted status.
Color or Trim Pattern Status Meaning
Purple stole Senior Council
Blue stole Member
Red stole Member with a Century of Service
Braided silver cord Master Alchemists
Gold stitched Caduceus Master Healers
Copper chevron Doctorate in Scholarly Discipline
Seal of Solomon Master Exorcist
So that is the regular White Council, but what about when Wardens are on duty at formal events? Do they wear the stoles or is their attire along with the grey cloaks, slightly different since they are suppose to be in a position to protect and keep order?