-const QColor Trace::DarkBGColour(235, 235, 235); // Quite light grey
-const QColor Trace::BrightBGColour(245, 245, 245); // Very light grey
+const int Trace::ColourBGAlpha = 8*256/100;
+const QColor Trace::BrightGrayBGColour = QColor(0, 0, 0, 10*255/100);
+const QColor Trace::DarkGrayBGColour = QColor(0, 0, 0, 15*255/100);