Buildsheets of a H code three speed car built in June 70 show the identification stripes as Green - White - Yellow. Green appears to be a lighter version than we often see used representing GRN on build sheets. The rear stripe is not part of the identification set so its not in the buildsheets or recorded anywhere that I know of. You stated that your stripe about 11-12" from the flange "looked" white. Did you take off the top layer and look below where it had not been exposed to the elements. Since the strips purpose is unknown it may be possible that drivelines for the same applications had different colors at the rear end of the tube since it could identify a particular machine used, worker, check or something we don't even consider worthy of a mark. I would reproduce what you can form from your original since it can be documented
Similar to the M code 4 speed though it appears that on that example the worker applying the stripes got the order a bit mixed up. We do see this from time to time.
Because it appears that they shared the same driveline I would suggest using the same green as on the driveline on the forward yoke of the driveline. Would also measure/identify the yoke at the rear. If the same applying the same green. Don't forget to burn the edge where the yoke would have been welded to the tube.
Hope this helps