One of my hands was blue. Dark blue and light blue. Is that frostbite?

Frostbite does not. Typically affect the entire hand unless there has been severe exposure, in that case having only one hand affected would be unusual too those are cases where both hand and both feet are affected from severe prolonged cold. Frostbite comes in stages, mild is irritated skin, then blisters then dark dark skin which looks dead. Circulation issues can give "blue" hands see your doctor.