base section Titles are invisible in dark mode

Change-Id: I46848169f9376588e91d9684e47f388074c41493
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/146997
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
diff --git a/vcl/source/app/settings.cxx b/vcl/source/app/settings.cxx
index 9762c21..71d58a4 100644
--- a/vcl/source/app/settings.cxx
+++ b/vcl/source/app/settings.cxx
@@ -2257,12 +2257,23 @@ void StyleSettings::Set3DColors( const Color& rColor )
    mxData->maDarkShadowColor   = COL_BLACK;
    if ( rColor != COL_LIGHTGRAY )
    {
        mxData->maLightColor    = rColor;
        mxData->maShadowColor   = rColor;
        mxData->maDarkShadowColor=rColor;
        mxData->maLightColor.IncreaseLuminance( 64 );
        mxData->maShadowColor.DecreaseLuminance( 64 );
        mxData->maDarkShadowColor.DecreaseLuminance( 100 );
        mxData->maLightColor = rColor;
        mxData->maShadowColor = rColor;
        mxData->maDarkShadowColor = rColor;

        if (!rColor.IsDark())
        {
            mxData->maLightColor.IncreaseLuminance(64);
            mxData->maShadowColor.DecreaseLuminance(64);
            mxData->maDarkShadowColor.DecreaseLuminance(100);
        }
        else
        {
            mxData->maLightColor.DecreaseLuminance(64);
            mxData->maShadowColor.IncreaseLuminance(64);
            mxData->maDarkShadowColor.IncreaseLuminance(100);
        }

        sal_uLong   nRed    = mxData->maLightColor.GetRed();
        sal_uLong   nGreen  = mxData->maLightColor.GetGreen();
        sal_uLong   nBlue   = mxData->maLightColor.GetBlue();