I changed the color theme on polyphone on my mac (sierra) to aqua and after the next start nearly everything is black and i can't recognize anything, and i tried to change it back with no success. I even tried to erase polyphone completely and reinstall it that also failed, you seem to save the preferences somewhere can you tell me how to reset the preferences?
I have the same problem. erased the preference files com.polyphone.Polyphone.plist and fr.com.polyphone.Polyphone.plist from ~/library/preferences
didn't work in the first place. So I erased the plist - files and the app itself, cleaned the trashcan and reinstalled polyphone1.8 now it works again.
I'm sorry for the delay I've been away for a while! On windows you have to launch regedit.exe and remove this node (right click -> delete): HKEY_CURRENT_USER -> SOFTWARE -> polyphone