I do have an Opuntia too, not sure what cultivar..pads turn pink when it is cold stressed:
Photo taken March 2014, early Spring
Such slow growing cacti, nothing happening for most of the time, but finally I got some new growth this summer...so I think that is how they multiply, either new growth from the base or new bumps maturing which you can clip off later and root. Just have to be patient like a saint, very slow growing. Got to give it lots of full sun.
a new growth also showing at the back:
more little bumps growing:
