Do you want to change the colour of an PanelBarItem, or the background image?
If the you want to do former, actually you don't have to do it, as the colour of the link is already black (#000000)
If the you want to do later, you need to create a custom background image and include it in the css. There is a very good article in the documentation about creating / customizing custom skins for PanelBar
All the best,
the Telerik team
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