Why won't my BMW dealer repair brake calipers?

I recently took my 2017 BMW 2 Series Active Tourer to the local BMW dealership for a 2-year brake fluid replacement. I was advised that the technician was unable to service the rear brake cylinders as...

Is there a difference in performance between colours on brake calipers?

Is there a difference in performance between colours on brake calipers? Is red, or green better than black for example? Does the motor industry have particular engineering standards that apply to these...