[pgreenwood]

Yes, it can happen due to alpoecia areata which can be stress related. I had a beard hair turn white almost overnight. I am normally clean shaven but a large section of my facial hair fell out at once and almost immediately grow back white. I think it took a few days but seemed to happen overnight. Also alopecia can tend to attack just coloured hair, so if you're salt and pepper and lose all the coloured you can appear to go white overnight.