This sounds like a condition called livedo reticularis. This occurs when medium sized veins under the skin have sluggish flow and become dilated, leading to a lacy, web like pattern of alternating white and darker areas on the skin. Livedo reticularis is much more common in women and it regularly occurs in colder weather.
Virtually all cases of livedo reticularis are not caused by medical problems, especially if it has been occurring your whole life. You can help the situation mostly be keeping your hands warm and avoiding exposure to cold weather. However, if the symptoms are worsening, if you develop any sores or ulcers of the skin in the affected areas, or if you have pain, then you should talk to your doctor
about the problem.
Sometimes livedo reticularis is associated with a serious underlying medical problem. Usually, this occurs in people who have not had it previously and then develop it later in life. The types of conditions that can cause it include various types of vasculitis
(inflammation of blood vessels) and connective tissue disease or rheumatologic diseases. For these reasons, if you are experiencing any other concerning symptoms other than the livedo reticularis you should talk to your doctor.