highlight and highlightText colors may revert to the default colors even if explicitly set in qtconfig, this would happen when running KDE 3.x only having one of those colors set via the KDE control panel. The reason for this is that Qt reads the ~/.kde/share/config/kdeglobals file by default when parsing KDE colors, but this is insufficient since the only colors stored there are the one that deviates from the default KDE colors. Qt then later does

if (highlight.isValid() && highlightText.isValid()) {

and applies the highlight colors in this block, but since only one of those were read (since only one of those would be set in the above mentioned kdeglobals file) the highlight colors are not applied.