As has been explained to you, Avianca agents are given a tool to use to determine entry requirements. Agents cannot possibly know every requirement for entry to every country for every passport for every residency status, for every possible type of travel document, for every country transited, for every health requirement etc etc etc. That is why agents are given a tool to use, and that tool is Timatic. It is not Avianca's problem if that tool is not correct (although you still have not proven that it is not correct). They do not and will not look at screenshots, consulate websites or anything else because as you have seen, there can sometimes be conflicting information. It is not for an airline agent to determine which source is correct. IATA has done that for them by given them Timatic. That is the only thing they use. Period.

If Timatic tells agents that a YF vaccine is required and you do not have one, you do not board. It is as simple as that. That is the end of the story as far as Avianca is concerned. They fulfilled their requirement of checking their official tool. If that tool is incorrect, your issue is with the agency responsible for that tool. Avianca acted in accordance with proper procedures and had a good faith belief that you required the vaccine according to Timatic (which again, is the ONLY source they use and are required to use) so any action against them is bound to fail. You have been told this yet you don't want to hear it and you are dug in. If the agent misread Timatic, that is a whole other story. But if Timatic told them you needed it, that is the end of the discussion as far as they are concerned. Every other airline would have done exactly the same thing with exactly the same result.

This is what Timatic shows as required for Colombia when departing from Brazil: