Calling ‘Cristata’ a cactus is a misnomer, as it is actually two succulents grafted together.
The wavy, coral-like top of the fan-shaped succulent is a mutation of Euphorbia lactea, and then grafted onto the root stock of another succulent/cactus. “Coral Cactus” ranges in color the one we have is pink.
The edges of the crests can turn pink when happily stressed. ♥