< Smiley with eyes a'glowing...

This shows what you can do by adjusting the transparency setting on the Object Manager, and tweening with that handy "Tween" function on the Frame Panel.

In the uga file for this, there is a black object behind the face, so the face darkens a little when you adjust the transparency a small amount. White circle objects for the eyes were added. The transparency for the eyes is what is tweened.

Viking's Web Animation