Futura paint can be difficult to match and is best done by a professional.
Aprilia do not release paint codes either.
Some colours are easier than others are available as touch-ups on ebay from a company called Bike Colours.
Flame Red would appear to be the hardest to match, made harder still by its tendency to fade, especially in strong sunshine. This makes it impossible to get a replacement panel to match exactly and there have been cases of owners refusing new panels because they thought they were the wrong colour.
Both Flame Red and Stream Silver are made up of four coats of different colours.
Of course, the Aprilia Futura has been knocking around a few years now and there are plenty of bikes with custom paintjobs. If you’re looking for inspiration you can see a selection in the photo galleries on this website.