How to Change Back to the Light UI Style used in the previous versions of ARES Commander?
Execute the OPTIONS command. Then move in the dialog to "System Options-->Display-->User Interface". Here you can enable the light UI style again. See also the attached image.
The current setting is stored in the system variable COLORTHEME. 0 means Light UI
1 means Dark UI
Please note, that you have to restart ARES Commander, so that the UI change comes into effect.