To highlight light fixtures in a particular lighting group, go to
Ribbon: DM Electrical->Lighting Groups-> 
Highlight Lights in Group
Pulldown Menu: DM Electrical->Lighting Groups->Highlight Lights in Group
Select Lighting Group Dialog Box
Select the Lighting Group to be highlighted and press the OK button. All of the light fixtures in the selected lighting group will be highlighted.
To remove the highlights, use the standard CAD REGEN command.