A default frame is transparent.

Toggle fill on a frame

Do one of the following:

•Press K.
The frame fill becomes black.

•Press W.
The frame fill becomes white (a color W is applied, if existing).

•Press CTRL+ALT+M.
The frame fill and border becomes as specified in your personal preferences.

•On the Area/Image colors palette, in Fill select Solid Color or other color options, and then in A select the primary fill color.