This is a toggle command that turns instant colonization on and off. Instant colonization, as you might've guessed, makes colonization instant. This command will also affect AI countries making them instantly colonize too. By default, typing this command will turn on instant colonization. If instant colonization has been turned on, typing this command will turn it off.
fast_colonize
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fast_colonize
If instant colonization is disabled (default), the above cheat code would turn it on. Otherwise, it would turn it off.