> I believe we already have the resources to colonise the Moon and maybe Mars right now.

That is or was essentially the mission of the US government's Artemis program, as I understand it. Some elements of the plan are (or were):

'Civilize' (my word) the Moon - build PNT, situational awareness, communication infrastructure, bases, permanent human presence etc. Bring it within a normalized region of operations, like Earth orbit (though obviously much more expensive and less utilized). A benefit is developing plans for infrastructure and operations on Mars, in a much more friendly and less expensive environment. What does it take to support humans efficiently and reliably on another body?

Also conduct experiments and develop technology for Mars in cislunar regions - again, much friendlier and less costly.