There are certainly some valid applications to a lunar colony, but none I can see which would justify the colossal expense and drain on resources it will represent. Perhaps the most obvious benefit will be in developing techniques for future, deeper missions, just as Mercury and Gemini were test beds for Apollo. Those were successful and valuable programs, but they were still dead ends. Even going back to the moon on an occasional high-priority mission makes more sense than a permanent base in one spot.

I would prefer to see these resources go into more low Earth orbit activity, such as additions and enhancements to the space station, or additional space stations in more specialized orbits specialized as launch points and vehicle assembly for planetary missions. This would be a multi-purpose use, with science, deep mission staging, training and technology development applications where more resources could go into the station and the missions and less climbing in and out of the lunar gravity well.

As far as the manned program goes, most of the time spent on future interplanetary missions will be spent in transit, and survival lessons learned on one world may not be very applicable to another. We need to develop a complete zero-g technology and deep-space capable vehicles and that can be done close to home a lot cheaper.