Thanks for the appreciation wealstarr.
You can achieve what you want by creating a piggyback skin.
<?xml version="1.0" encoding="utf-8"?>
<root dependsOn="Sportura Pinstripe.xmlc">
<colours id="Default">
<element id="Content[Artwork].ScrollBar.Lowlight" bg="31,31,31" bg2="31,31,31" />
<element id="FilterPanel.ScrollBar.Lowlight" bg="31,31,31" bg2="31,31,31" />
<element id="ColumnBrowser.ScrollBar.Lowlight" bg="30,30,30" bg2="30,30,30" />
<element id="Panel.ChildBody.ScrollBar.Lowlight" bg="31,31,31" bg2="31,31,31" />
<element id="Panel.ScrollBar.Lowlight" bg="31,31,31" bg2="31,31,31" />
<element id="LeftNavigator.ScrollBar.Lowlight" bg="31,31,31" bg2="31,31,31" />
<element id="TrackInfoPanel.ScrollBar.Lowlight" bg="31,31,31" bg2="31,31,31" />
<element id="NowPlayingList.ScrollBar.Lowlight" bg="32,32,32" bg2="32,32,32" />
</colours>
</root>
P.S.
I just edited the original skin to use slightly thinner scrollbars.