Thank you Clabro, your view and statistics kind of line up with my gut feel.
Either "blue" or "red" M brake kits are quite expensive, and the performance benefit of such upgrade is probably very modest at best. Granted, one must not discount the visual appeal of colour calipers/bigger rotors.
I have been trying to get my BMW dealer to share with me the number of "red" retrofit kits they sold and/or installed in the past couple of years, but they just would not do it. Proprietary info, I guess.