Methylene blue hydrate is a different dye to regular methylene blue. Although methylene blue is a hazardous chemical, it is used in a dilute solution as a stain in microbiology and as a redox indicator in Chemistry (for the “Blue Bottle” demonstration with glucose solution).
The two chemicals are similar, but in different forms: the hydrated one is used in medical treatments via IV or the like, so they have two different CAS numbers and different properties.
Methylene Blue hydrate is on the banned and restricted list.