Post-call dialog rating buttons aren't obvious enough

After a call is over, in the dialog that appears and asks for feedback on the call quality:

The three options (sad face, neutral face, smiley face) are not very clear. The face art looks nice aesthetically, but takes some focus to understand what each one means. This is exacerbated by the fact that each one is the same gray color until you hover over them, and there's no text to reinforce what the face means.