Yes, if you're adding a colleague to multiple groups on the HIGH5 platform, you will need to pay an additional fee for each group they join. The fee structure for team reports operates on a per person, per report basis. This means that each individual's results are uniquely incorporated into the team report for each group they're part of.
If you don't want to pay every time you add a person to a team, you can consider getting them a full platform access.