Made yellow slightly redder for pen on white background

src/core/UBSettings.cpp

@@ -265,7 +265,7 @@ void UBSettings::init()
     pageDpi = new UBSetting(this, "Board", "pageDpi", 0);
 
     QStringList penLightBackgroundColors;
-    penLightBackgroundColors << "#000000" << "#FF0000" <<"#004080" << "#008000" << "#FFFF00" << "#C87400" << "#800040" << "#008080"  << "#5F2D0A";
+    penLightBackgroundColors << "#000000" << "#FF0000" <<"#004080" << "#008000" << "#FFDD00" << "#C87400" << "#800040" << "#008080"  << "#5F2D0A";
     boardPenLightBackgroundColors = new UBColorListSetting(this, "Board", "PenLightBackgroundColors", penLightBackgroundColors, 1.0);
 
     QStringList penDarkBackgroundColors;