I made a quick search and didn't find a specific RAL number. However, a few of the Australian and U.S. sites indicate it is the same orange paint as the late model Kubota tractors.
When I refurbished the 2 Hegners, I resprayed with an off the shelf Orange which was as close as damn to the Hegner colour.
That was a number of years ago and when we moved I turfed out all the half full cans of spray paint.