how can I add Members of a Groups (JCVA Color Guard group) to event participants for a Color Guard event
if you carry out a contact search (selecting the group your interested in) and select all of the results, one of the actions you see in the actions menu will be to add them to an event (Register Participants to an event). Have you tried that approach?

Once registered you'll be able to carry out all the tracking/reporting you've highlighted.