Desktop keeps going blank with a bright red background

Hi

I am finding that my desktop is going blank and BRIGHT RED when somebody connects to my screen. As I have two monitors it is displayed across two monitors which is pretty annoying and was shocking at first.

I need to either change the colour OR stop the desktop from going blank.

I have checked Extras > Options > Remove Control and the setting "Remote remote wallpaper" is disabled. This is the only setting I have found that I think might have an impact. If there's a setting I have missed please let me know & point me in the right direction.

All help & advice is appreciated,

Many thanks