Switch between background without losing preview

Is it possible to switch between background to foreground, and keep the fill on, I’d like to do this to compare back and forth, thanks.

I am not sure I understand what you mean. Put the cursor to the left of the glyph in question and press cmd-B while in text mode (T). Fill will be preserved unless you have a different setting in View > Fill Preview. You can type several instances of the letter next to each other, Background will only be shown for the current one. This way you can have back- and foreground side by side.

Thanks, that should do it!