‘De una’ in Colombia is used to mean ‘ok’, ‘I agree’, ‘sounds good’, ‘ready’ and ‘right now’, depending on the context. It’s something I’ve been hearing from my Colombian friends for a while and even though I understood it by context, I never bothered to look it up…until now. As for its origin, I would guess it comes from ‘de una vez‘ (at once).
Ex. Entonces nos vamos al concierto? De una, parcero!
Ex. So we’re going to the concert? Sounds good, mate!