I see what you mean. It's meant to be grey is unpaid (boooo), paid is green (yayyy), but to your point it might be better as unpaid green (yay sats await), paid grey (boo sats spent).

Representing state in a single icon is tricky. Should the representation be its current state or its potential state? e.g. if I'm in light mode, should the icon to switch to dark mode by a sun or a moon?

Most UX people seem to believe it's the current state. I tend to like potential state which kind of speaks to your preference.

The motivation for the way we did it was being able to tell at a glance, when looking at a list of a user's bounties, if they pay their bounties or not.