I'm sure this has been covered but I missed it. The few places that I play use the red circle ball for the most part. The other day the rack I got, had a cue ball with a blue marking. This cue ball seemed heavier to me. What is the difference between the 2 cue balls--weight wise? I know for sure that I had to have a much purer stroke and hit a tad harder to do what I normally do in a 60 minute workout.