Blue= LEO (now also public service)
Red= Gen population
The labels have nothing to do with capcity of magazines however if you buy Gen3 Glocks in compact and full size, the red labels have 2 mags while the blue have 3. All Gen3 sub-compacts only come with2 mags regardless of label. The Gen4's now all have 3 mags. Each gun store has had their blue labels seperate to meet immediate needs to LEO's.