On-screen buttons turn to white
 

I have been working on a model and have put on-screen buttons to
activate macros. Things have been running normaly, but today I find
that the buttons have lost their gray background color, and are now
white outline rectangles with rounded corners with the labels as
before. They are still objects and they still work. This happened
after I deleted some styles in the model, so there may be a
correlation between that action and the buttons' current appearance.

I'd like to get them back to their original button appearance. Saving
and reopening the file did not change them. Would I have to rebuild
the buttons? Any help would be appreciated.