The orange color found on driveline ends/yokes does not apply to all years for our classic years and method of marking the end yokes is not the same for all years and applications either from the examples I've found and documented.
Yokes were often identified by a color code so that workers assembling the drivelines could choose the correct front and rear yokes for the driveline they were building. The station likely had dozens of different ones and like other things related to our cars a color identification was the quickest way for a worker to identify the right piece quickly.
As for driveline markings you have identification markings for the worker on the car assembly line so they they could locate and install the correct one for a particular car while there is often additional stripes and markings identifying other practices and checks that were applied during the driveline assembly process
