Raynaud's
As everyone has said, it looks like you have Raynauds. The mottled look is a classic finding. The important thing about Raynauds is that it can be associated with other illnesses, which you should see your physician and be evaluated. Your doctor will know what to ask but some of the other important symptoms are rashes, muscle pains, joint pains/arthritis, headaches, urinary problems, and others.
As for prevention and therapy, a lot of good advice has been passed. As well as the feet, it is important to keep the whole body warm. The body functions to preserve the heat to the central organs, and if the vital organs feel cold, it can cause vasoconstriction and in the case of Raynauds, vasospasm. The conditioning therapy has helped many, but the studies that have been conducted are pretty weak and the results vary greatly. You can give it a try, but it might not work. As for medical treatment, it depends on why you have Raynauds. Your doctor can help tailor the appropriate therapy if the Raynauds is secondary to another problem, such as peripheral vascular disease, neuropathy, or lupus. If it is just isolated Raynaud's, as one person has already said, nifedipine is a very good drug with few side effects. If that doesn't work, your physician can add other vasodilators to your therapy as well. Hope this helps.