As to white hair caused by poor saddle fit, there is almost a 100%
chance there is also underlying muscle damage. The injury may be minor
but the extent of involvement should be identified. Then you can go to
work on a recovery strategy.
One last thought, shoulder and back problems may manifest themselves in
the lower front legs, you know, bowed tendons, suspensory pulls, etc.
Accordingly, white hair is really a red flag.
Ramey and Cynthia Peticolas-Stroud