Chevron. I know little of Airbus operations (or any heavy operations for that matter) but venting fuel on a departure at 3000Ft would certainly be cause for concern. I think.
Perhaps it was water vapour. If the Temp was +30C then by 3000 i think he might have been in air that was sufficiently humid / correct temp to turn to vapour over the winglets?
Or maybe you are entirely correct and i am talking absolute
K