Some of my superworms are white! Is there something wrong with them?

This is perfectly normal. Like other insects, superworms shed their exoskeleton (outer shell) periodically as they grow, a behavior known as molting. Freshly molted superworms are creamy white in color and are very soft, but they will return to normal color and hardness in a few hours as they dry out.
Try feeding a freshly-molted superworm to your reptile or amphibian as a special treat! Many reptiles and amphibians seem to prefer these extra-soft feeders.