The people problems are enough to sink the idea. The technical problems are staggering.
In a recent posting, I wrote a short story about what would happen if we had a colony on Mars and they had a child from hell. It is not an absurd proposition - we have crazy people and plenty of them, here on Earth. All it would take is one malcontent on Mars to destroy the entire colony. On Mars, you could not have 9/11 truthers, incels, proud boys, flat-earthers, anti-vaxxers and other delusional people. No crazy billionaires - or even capitalism! Even 2nd Amendment nuts and "Free Speech Absolutists" would not qualify, as the environment would be so harsh as to require that everyone follow orders and work like dogs in a military-style dictatorship. And you have to hope the dictatorship doesn't go off the rails, either - as they tend to do.
No, we are not cut out for Mars. Maybe that is why robots do so well there. Maybe our robotic AI descendants will settle there - it is a perfect environment for them, I think.
But this is not to discount the technical problems involved. And to begin with, we have to define what a "colony" is. It is some outpost that is constantly resupplied by rockets from Earth, or a self-sufficient closed-loop system that can survive on its own? Many posit that colonizing Mars is essential to the survival of the human race, as we have screwed up things here on Earth so badly that it is only a matter of time before Putin, Kim Jung-Un, and/or the Iranians start WW3 by throwing a few nukes.
And statistically speaking, they are right. The probability of a nuclear war starting in any given year is a finite number. The more nations that acquire nuclear weapons technology, the higher this probability becomes. But for any finite probability, integrated from 0 to infinity, the probability turns into a one - a certain outcome. It is a matter not of "if" but "when" someone gets desperate and decides that maybe "a little nuke" won't be so bad. Perhaps soon - if Putin feels backed into a corner. Potential successors are just flying out the windows - he realizes his days are numbered anyway. Why not go out with a bang?
I digress yet again. But the "people problem" here on Earth is the same "people problem" on Mars. Could we have a Martian colony with people believing in end times theology? Or even religion of any sort? Because when rational people base their decisions on irrational beliefs, all hell breaks loose. The people problem won't go away by colonizing Mars - even if it was technically feasible. And it isn't technically feasible.
NASA is making noises that the Chinese are going to colonize the Moon and lay claim to it. No doubt this is an angle to get additional funding - staring a new "space race" to land on and eventually establish an outpost there. Note I said an outpost and not a colony. It would be at least a little more practical to establish an outpost on the Moon, as opposed to Mars, as the cost (and time needed) to hoist supplies out of our gravity well and to the Moon would be far less than the cost of sling-shotting mass to Mars.