Their point was that if language async is a color, so are async callbacks, which are arguments, therefore arguments can be colours.
What some people want to do is call every argument a "color", that is, I changed this function to have to take a Username and now it's Username-colored is the claim. I supposed I should have made that more clear. This provides a definition where that is not the case.
GetUserByUsername needing a username isn't a color because that's just what the function does, but GetFontSize needing the current username (to look up their preferences) is one if you don't make it a global variable.