I've tried to find a way to change this numerous times too
. I'm not sure it possible from any examples I've found anywhere either. You've probably looked here already, but this is the only place that even had something close:
This is what is there:
<color id="common.itemlist.outline.current" value="255,255,0"/>
<!-- Currently playing outline color -->
<color id="common.itemlist.outline.focus" value="0,128,128"/>
<!-- Focused item dashed outline color -->
Have you been able to change the other colors in that window already?