I will ask my doctor about it. When I elevate my legs they do go back to normal color.
It could be a circulatory problem or something different like Raynauds. I have Raynauds and my feet and hands turn a nasty gray/blue when they're cold or if I sit or stand too long (my feet then). Do your feet improve when you elevate your legs? I do hope you'll be asking your doctor about this since it's not a normal reaction. If your doctor thinks it's Raynauds, be sure to see a neurologist too to check for secondary things like lupus or RA.