I just hatched 8 eggs from a pair of Black Sumatrans Python curtus. I got the pair as year old snakes, so I don't know what their heads looked like as babies-but both male and female are pretty black on a light to dark scale and have nice black heads. The female is shown in the photo to the left sitting on her 8 eggs.
Of the eight babies, two have super black heads, one has a lighter head (it is in the photo below with one of the babies with a very black head), and 6 have pretty black heads, and look like the single snake seen hatching on the left. When this first snake hatched I thought it had the blackest head I'd seen on a baby-until the two really black headed ones hatched!
Notice in the photos below that the baby with the really black head has no orange in the eyes-both hatchlings with a really black head just have a straw white-pale yellow in the eyes-no orange. I am wondering if the mom who has orange eyes, started out looking like the 6 babies that have pretty black heads and orange eyes-and her head got really black as she matured. It would be neat to see if there are Black headed Sumatran adults out there with these light colored eyes. Maybe that is the key to making ALL babies that hatch have the super Black heads!