You might consider the costumes of the people as a clue to recognize the dances. Also depicting a unique hold -- like the corte in tango; the leg flicks (or whatever they are called) in quickstep; the New Yorker (crossover breaks) for Cha Cha; the contra checks in Rhumba, etc. You might be able to find one unique pattern/hold in each dance that you wouldn't find in any others and if it crosses over to another dance, the costumes could give the viewer an idea.