Hello Meghan23,
We are volunteers here and not medical professionals. We have a lot of experience with Type 1 diabetes.
Has your son been diagnosed with diabetes? I ask because it's not clear if he is diabetic or if you ended up in the wrong forum.
In general, I'd suggest you work with your doctor and follow his advice. Ask him what this 'condition' is called so you can read up on it and ease your worries. If your son is diabetic, I'd recommend that you check his blood sugar when his lips turn blue and his hands & feet feel cold.
Finally, evaluate his clothing relative to the weather. Perhaps providing him more layers on his trunk (where most of the heat is generated) and ensuring he wears a warm hat (most heat is lost from our heads), scarf, gloves & socks may also allow his little body to keep all his parts warm.
My oldes daughter had the same problem starting when she was an infant to age 4.
What it is, is that thier nervous system isn't matured until around age 4 and some children have a problem, especially during winter, regulating thier temps. Its nothing to worry about and it will go away. you can try putting socks and such on your child, that may help. My daughter is now five and doesn't have anymore problems.