OK I must write this down as I should ask Hilaire for help the third time about this simple task.
For my poor eyes, the Dr. Geo sketches do not look very
clear in the default dark background. This is how you change the background to
white: click on the workspace background to bring up the system menu. Open the
"settings" dialog. Click on "style". Change the "User Interface Theme" to
"Light theme". The change takes effect immediately. Now you have a white
To make the change permanent, again bring up the system menu Then click
"tools" => "Save Session".