The masks used by actors were usually emotionally ambiguous depicted exaggerated, emotional facial expressions were all the same were only used by an actor playing a god

The masks used by actors depicted exaggerated, emotional facial expressions.

In Greek theatre, masks were created to exaggerate expressions as well as the actor's facial features due to the fact   the audience members were sitting to far away to notice the expressions from the actor's bare face.

This also allowed actors to play a wide variety of rolls, for example: playing a female/male character.

The masks also were worn in order to distinguish emotion, personality and age.

b: to eliminate competition from other farmers