You should be able to change your kit without losing your group MID RIDE. In that way if you find a group, then you can change into their kit too.
You can do this by hitting “P” while riding, and putting in the promo code (that you’ve probably already used to get the jersey) to set up a new kit.
You can’t do this (yet?) with the default kits, but for the custom kits you can. I verified this tonight with my daughter’s profile as she was riding the course.