Listo

Listo
 

I know it means ready when proceeded with estar and smart when proceeded by ser, but I have seen it to mean de acuerdo. Tiene que estar allí a las 7. ¿Listo? Listo

Is this a common usage or one unique to Colombia?

I don't know if it's regional usage, but it would be understood in context in Mexico.
It would be like saying: "¿ya está?" It's an informal way to make sure we agree, like "are we on the same page?"
However, a Mexican would probably find both "¿Listo?" and "¿Ya está?" a bit impolite, depending on the tone. :D
We might ask something like "¿Está bien?" or simply "¿De acuerdo?" Some younger people tend to use "¿Vale?", which is imported from Spain. Older ones, like me, might use "¿Sale (y vale)?" :D

Listo meaning OK is used by gangsters mostly in the awful Colombian miniseries I am watching. I now assume it is, for the most part, impolite in Colombia too.

Thank you.

Oh, if it's an order, it's understood as "you better get it right" then. :D