I have just corrected my post #22 to show that only VH-ECE carried the orange scheme. VH-ECF was sold in 1972.
FrogNtoad
It was my understanding that the orange scheme was to make the aeroplane more visible during radar tracking exercises under contract to the military although your explanation is equally feasible.
For more info on the HS125s
If anyone knows the current owner of VH-ECE, please lean on him to do the right thing with this aeroplane. Pick a museum - any museum.
Rgds