Unfortunately, this one was only a short-lived phenomenon. One cane of my Granada started blooming with stripes. I tried to root some cuttings, hoping to grow a striped Granada sport, but they didn't take.
After I had acquired Caribia and Harry Wheatcroft, I learned they were actually the same rose, so here's another photo of Caribia, but this one's the rose labeled 'Harry Wheatcroft':