Go right ahead! Hydrangea macrophyllas should be pruned after they bloom. Reblooming hydrangeas are actually more likely to develop flowers again later in the season if you 'deadhead' them just after their first flush has run its course. Be sure to cut your stems just above a pair of leaves (or at any node) for the most success.

Thanks for the tip. I read on a website yesterday that it was ok to prune as well so i went ahead last night and pruned them up. No longer does my twist n shout and blue original look silly! :)