What Could Cause Purple Colored Hands While Having Excavating Business?

Hi. My father is 87 yrs old and is pretty much active for an 87 yr old. He came by yesterday and his hands were purple. What could cause this? This morning my brother checked on him and his hands seem to be normal. I am concerned. He is still driving and has his own excavating bussiness. I know he has an enlarged heart and the starting of emphysema which he was told could have come from the gravel over the years. He was and never was a smoker. Please help.