I run Compare. The files which are equal in the folders not shown anymore. Now I do something else let me say write a mail. Come back to FC and see that some files are missing. I have no visual feedback that FC runs in Compare-Mode.
I can get in panic now

Is there a setting to change the background color when in Compare-Mode? Haven't found any setting.
Anyhow it should be possible to get back to normal operation by click on just one Icon or have a Key and not do a Refresh twice means in each pane.