It's called "reduced pattern" when you see that. It's not a "morph" usually. There are genetic lines of reduced pattern, but more often than not, it's just a natural selection of normal genes that gives that appearance. Really nice reduced pattern females are often prized as breeders because their pattern sometimes influences the babies, even though it's not a predictable genetic result that you can call a "morph."
"Normal" ball pythons come in a huge range of both patterns and colors.