Groups and Items in Panel Menu are highlighted once you hover on them.
But the model to influence this behavior is quite inconsistent:
a) the only place you can redefine @hoverClass is Item
b) the items and groups get "rf-pm-itm-hov" class when hovered, but this averts to change styling of Group hovering in comparison to Item
1) add new class "rf-pm-grp-hov" to classes with same initial styling as "rf-pm-itm-hov"
2) add new attribute @hoverClass to Group to add custom classes to group when hovered
3) add new attributes @itemHoverClass and @groupHoverClass to Panel Menu to define style classes in scope of whole Panel Menu