The Moon is not "colonizable." It cannot support life. Life there would require constant deliveries of water and air.

Neither is Mars, but less absolutely so. Mars has water, mostly in ice. Theoretically, this means it could be "terraformed" - made Earth-like, able to support life. It is possible it once was able to. However: 1. this would take thousands of years, and 2. Mars is unable to keep or "hold onto" an atmosphere because of its lack of a magnetosphere, so it would have to be constantly regenerated. The costs and timescales involved are enormous, far beyond even Musk.

We won't be "colonizing" Mars in any of our lifetimes, if ever.

A manned mission, though, would be scientifically enormously significant.