NavBars come on two layers and use Theme colours.
Solo MouseOff layer and on the Colour Bar, open the Colour editor, select a Theme colour and swirl around.
Do the Same for MouseOver.
Double-click the NavBar and click the Ungroup to edit graphics and you then have full control over the button design.
You have to select all the buttons and use the context menu to re-create the NavBar.
The Help is very comprehensive.
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