how to have the background black or any other color than white
With one of the standard styles:
menu Window > Styles > Edit > Background Settings (third icon) > change the background to black and uncheck ‘Sky’ and ‘Ground’.
wonderfull thanks for your prompt help
And for that - and other - settings to become the basis of your default SU model setting, create a file with your preferences you want to see then go to File > Save as Template. Tick the box to make that your default. Of course, you can change templates at will from Window > Preferences > Template.