The 'blended background' checkbox is checked under View/Display Settings/System Colors.
To make your system come up this way every time, save the settings of the SYSTEM COLORS dialogue box by selecting File > Save in the dialogue box. When asked where to save the file, pick a stable place you know. Then add the path to your config.pro something like:
system_colors_file /share/ptc/pro_stds/configs/syscol.scl
The command in the system colors file controlling the background is:
BLENDED_BACKGROUND no
(source:
THANKS- IN THE MEAN TIME I SET UP A MAPKEY- IT'S ENTERTAINING- AFTER PRESSING THE BUTTON ALL THE COLOUR SLIDERS MOVE THROUGH COLOURS I PONDERED BEFORE SETTLING ON THE FINAL SCHEME.