Ganymede is the largest moon in the solar system. It is possible to colonize and terraform Ganymede. Ganymede has salt water ice. But probably by the near future, people would probably remove salt before it could be drinkable. Ganymede could have a subsurface ocean. If there was life, colonists would have to avoid it. Ganymede is not in the radiation belt. So it could be colonized on the surface.
Ganymede
Nederlands; Kolonisatie van Ganymedes