I dont know about Tiger Barbs, but Cherry Barbs do dance around in a circular motion when they are about to breed. The male is normally bright red too.
I will try and find out for definate for you the breeding habits to see if we can nail the issue.
Edit: Having done a little digging, it looks to me that they are most certainly mating: check out this video. Is this what you are describing ?
when i was going to try to breed tiger barbs i found out they are egg scatterers so they do chase each other about but to successfully get them to hatch you have to get the fish out away from the eggs or they quickly eat them thats what i found out anyway
Havent watched the vid, but tiger barbs do this all the time, sometimes its a dominance issue, working out the pecking order of the group. Great fun to watch - Oh I miss my tiger's