Sure seems to me that any thoughts of colonies on Mars, with its present climate and low pressure atmosphere, is merely a pipe dream. That's a one-mistake-and-then-you-die place for humans with little in the way of resources that don't require huge amounts of energy to utilize.

I think if we've got grand plans for colonizing any other planet in our solar system that we have to think even larger - moving the entire planet to a more compatible orbit. The energy required is incredible but at least the work to do it is focused on changing just one thing. Mars needs to get closer to the Sun to bring up its average temperatures if we have any chance at all of making it hospitable. Venus needs to move farther away from the Sun to cool it down a bit to start the terraforming process. All in all though, we need whatever planet we decide to persue to be closer to us so that the trip back and forth is a matter of days.

Both planets need a restructuring of atmosphere to make them liveable. Whether Mars, with it's low gravity, can support a thick enough atmosphere for human life is unknown. Venus has too much atmosphere. Maybe it can be used as a propulsive device by blasting excess off into space.

I have no clue how planets can have their orbits changed and what effects it may have on Earth to have Venus or Mars millions of miles closer but it's a fun scenario to think of. Imagine the night sky.