What is the pattern for displaying the state of a thumbs up thumbs down button pair?

I'm looking for a pattern that clearly lays out how to make the pair of buttons look clickable (or tappable) in the following states:

• Nothing has been selected yet
• One of the two options has been selected

I want it to be clear to the user that they can change their mind and tap the other button, but I also want to make it clear which option they have selected.

Side note: I've always found toggle buttons with only two options to be problematic. Three is much better since the selected option stands out, but since thumbs up and thumbs down have become more standard, I am using thumbs up/down.