You can set the the background colour of scrollbars with ScrollBar::setColour (int colourId, Colour newColour). This works in lookandfeelV1 and V2 but not in V3. The reason is that the line
g.fillAll (scrollbar.findColour (ScrollBar::backgroundColourId))
is missing in LookAndFeel_V3::drawScrollbar. It's the first line in V1 & V2.
Is this an just an omission or a deliberate (aesthetic) decision? I just want to give my scrollbar backgrounds the same colour as their surrounding areas.