How realistic is the method of colonizing Mars in Red Mars by Kim Stanley Robinson? Specifically, the part in the beginning, with a 4 person crew to visit the planet first, sending crews, etc. Really I only care for the first visit and the 100 colonists, until other people came.
It's been a while since I read it, but as I recall one of the points of the book is the relative realism of the method of colonization. That is not to say that it is the best or the cheapest way of colonizing Mars. But given enough will and resources, we could pull it off with current technology.
Now the timeline of terraforming that occurs in the next two books may or may not be realistic. There's some debate about that.
It's been so long since I read those books so I may be off the topic here, but...; it would be much easier to establish a permanent station at/on (insert location here) if the people you send there never return. The space you would have had to spend on return fuel/supplies can now be used for more supplies to build a bigger and better station. Once the first pioneers build the initial base station subsequent trips can bring more people and supplies to build on that.
For comparison think of the colonization of the Americas. Most of the initial colonists went there with the assumption that they would never return to their home countries. Granted the Americas were more hospitable then the Moon or Mars would be, especially at first, but the idea is the same.
As to the technology to visit Mars, we've effectively had that since Apollo. Using that level of technology, we could have sent a manned mission to Mars with a reasonable chance of getting back alive. It would have required several launches with Saturn V class rockets, but it could have been done.
Establishing a permanent base there we could probably do at our current level of technology (though it would look quite different from the one KSR describes, and be smaller). It might not be self-sufficient however, at least not initially. But then, neither was the initial colony described in Red Mars (though to a larger degree than I envision a first generation actual colony based on current or near technology to be).
We of course lack the longevity drug that made the settlers in KSR effectively immortal (mind, I don't recall whether they were treated with it before or after forming their colony).
What is not realistic is the need of resources from Mars. Everything has an economic viewpoint. The whole purpose of people going to Mars was profit and is very difficult to make a profit even if you would harvest pure diamonds. Probably not even from moon is not profitable and wont be for some time. In terms of space and colonization territories Earth can support still up to 50 billion people without having to build an atmosphere or to take the risks of space travel.