Stenocactus is the genus, you mean which species it is. The flowers look a bit yellow, but I guess they are white with a pink-purple midstripes? These are difficult to identify, so do not expect a definite answer unless a Stenocactus expert comes by. I think it is a S. obvallatus, but there are forms of S. phyllacanthus that looks like this as well. A third possibility is S. crispatus, but it usually has more spines.
Thanks and sorry about the genus/species thing.... I know better. The flower color pictured is pretty close to true color aside from how it may appear on other individual monitors. I'll try to post another pic with better color balance.
Here is another pic of the flower with as true color as I can get. It is somewhat bronze/pink with cream.
Strange color, I have not seen that before on a Stenocactus, nor does it fit the descriptions I have read. The flowers on crispatus and obvallatus are white with purple midstripes, and phyllacanthus has yellow flowers except on a variant with flowers like those of the first two. Whether your plant is a hybrid, a mutant or just a unusual but natural variation I cannot tell, but I think it is worth keeping.
