Switzerland has incredible trains and train networks. Just before people chime in with "Trains are good but mountains are too much of a challenge so might work in other places better with a flat geography".

Sounds reasonable until you see how the Swiss do it. Nobody said that but that's where I feel this conversation is going and the previous commenter did say 'buses first'. Probably to exploit the existing road network and achieve ambitious goals in a piece meal manner.

Colorado is five times larger and has a much smaller population.

Which should make construction much easier, faster and cheaper due to lack of expensive private land boyouts.

Almost none of that population lives in the mountains.

Colorado is half Switzerland and half Kansas. Literally everyone minus a rounding error lives on the flat part.