The very first two screens in the live have their colors in the isolinux directory. One of the main background colors, once the images are changed, are setup in the gfxboot.cfg file. So if the background is still half purple, it has to be setup there.
From rafaellaguna, for Bento:
The contents of the
file must be these:
foreground=0xFFFFFF
background=0x958884
screen-colour=0x000000
hidden-timeout=2
label normal=Normal
append normal=
label driverupdates=Use driver update disc
append driverupdates=debian-installer/driver-update=true
applies driverupdates=live live-install
label oem=OEM install (for manufacturers)
append oem=oem-config/enable=true
applies oem=live live-install install
I will also try:
hidden-timeout=0
to get rid of the first screen with the 2 icons and see what happens.