Dear Mam, thanx for asking and trusting us at Health care Magic. There are various causes for Purple or Blue toes 1) Trauma 2) Cold - induced injury 3) Raynaud s phenomenon 5) Abnormal ( Less oxyngenated) circulating blood - 6) Decreased Artertial flow to the lower limbs 7) purple or blue toe syndrome 8) Diabetes Now coming to your question. Diabetes can cause foot/ Toe colour changes but it takes quite sometime for those to occur,.. so we don t expect significant blood vessel changes normally in newly diagnosed diabetics. so I feel its mostly related to cold..as you also said he works outside and at -6.. so no worries that said a proper foot care is must for diabetic especially when you are working in extreme temperatures hope this has helped you Dr.Samuel