Tephrocactus alexanderi var. geometricus

We have a nice little clump of Tephrocactus geometricus (syn.: T. alexanderi var. geometricus)  which was flowering for the last couple of days. The flower doesn't show it's true colors, as it has a slight pinkish cast and a darker mid-stripe on each petal. New segments, like the one to the left, are purplish to begin with.