To edit the style sheet you can use the css editor on module: CAT_StoreSettings: Enable the checkbox: [Edit Style Sheet of the selected Skin (click on [Update Store Settings] after you have changed the skin selection)]. There you can modify the css style sheet attributes: colors, background images etc. All tags are described in the css file text.
You can find the tags for the solpart menu in section: 'Style for the solpart menu in module CAT_MenuNF'

A detailed description of all paramteres can be found at: http://www.solpart.com/ .

You can find the aliases for all solpart parameters in the menu.ascx skin file.