A Zelonite
Without hat
Zelonites were a humanoid species and members of the United Federation of Planets during the late 23rd century. Zelonites were distinguished in appearance by their blue skin and tall stature. (Star Trek VI: The Undiscovered Country)
The Special edition DVD suggests these are "Andorians" who forgot their antennae or white hair.
The name for this species was never mentioned on screen, but is derived from three background sources. The call sheets for the scenes in Star Trek VI list the two individuals as Zelonites, one of the actors, James Mapes, lists this part as a Zelonite on his resume, [1] and It's A Wrap! sale and auction sold parts of the costumes on eBay and gave continuity photographs during the production as the source for this name. [2]