I own a 77 Archer. White with the Piper Blue and Gold stripe design. The paint work will have various shades of each colour caused by ageing and sun light. The paint underneath will probably be similar to the original. That on top is now probably a unique colour.
In the UK (and previously EASA) there is no stipulation on where you source your paint from, only that the job needs to be signed off as safe by your Licencing engineer. Consequently I've sourced all my paints from a classic car dealer and his approved paint supplier.
Take an area of each colour (if you can) and get them computer matched. However, take care on who does the matching as I've had some companies simply look at an inspection panel, nip out the back and come back with a perfect match, to others who needed three days and sold me litres of complete garbage that had to be thrown away. Find your nearest automotive paint shop (one that does high end cars) and ask who they use.
An aerosol touch up paint is unlikely to match. That said, the Blue on mine is a straight Dacia colour.