Colonies (with actual people, just adding, empty colonies produce nothing) produce infrastructure as trade good constantly. It gets turned into actual infrastructure when there's need. Production is shown on Wealth\Trade tab, every colony, even most smallest, produce infrastructure.
I get complaints about overcrowding all the time, but on the colonies where I need working workers I also put the Military, they put out any unrest. Terraforming works, but not always, sometimes there's not enough temperature to make colony fully habitable and sometimes there's things like on second attachment.
Also, civilian shipping SHIPS civilian infrastructure to overcrowded\almost overcrowded colonies, so your average Venus if you put any citizens here will turn into infrastructure sink, while also making all freighters busy.