Colombia does require a negative Covid test for entry. If it’s impossible for you to take one they allow getting one in Colombia and quarantine until the results are in.
However, I have not found any mentioning of quarantine requirements (positive or negative) if you already have the test on entry.
The US embassy states https://co.usembassy.gov/covid-19-information/#:~:text=Quarantine%20Information
Are U.S. citizens required to quarantine? Yes.
But it’s unclear whether this is a general requirement or only related to lack of testing.
Any other resource I found doesn’t mention quarantine or only in context of “no test”. However, I haven’t seen anything that specifically states: “No quarantine required if you have a negative test”.