Medicare does not offer a preventive benefit for E&M services (other than the limited IPPE and AWV), regardless of whether it is a facility or professional charge - Medicare covered preventive services are limited to just those that are specified in the regulations, which in this case would be the colonoscopy, but not any associated preventive E&M service. In order to meet coverage requirements, an E&M service on a different day would have to be medically necessary for treatment of an illness or injury, so if the service was purely preventive in nature, it would not qualify for coverage.
A routine pre-op E&M for an otherwise healthy patient is a component of the global package for a colonoscopy. Many gastroenterology practices safely evaluate their patients for a colonoscopy with a phone or written questionnaire, and with a physician evaluation just prior to the procedure, and only schedule the patient for an in-person visit if there are issues or comorbidities that require a more extensive evaluation by the physician. Because this is a common practice, in my opinion it would be difficult to argue for the medical necessity of a separate E&M visit for every screening colonoscopy patient unless there are documented problems that require that service.