I don't know why being cold seems to accompany RA, but I hear you. Sometimes, I think being in pain makes you more susceptible to cold. One of the things that have helped me with this problem has been gaining a bit of weight - the skinnier I am, the more cold I get. As well, I found that Tylenol Extra Strength helps me keep warm - I have no idea why, but when I'm not in a lot of pain and therefore don't take Tylenol, I'm more cold. The rest of the time, I wear sweaters and have recently decided to combine my need for warmth with developing a personal fabulousness, so I'm buying funky scarves. Wrist warmers are also in fashion right now - if you know a knitter, there is a great free pattern here (and Google will help you find all kinds of fancy patterns with beads, etc.), but you may also be able to find than at craft fairs.
That said, I did have a bell go off in the back of my head when I read your question, especially when you mentioned your fingers getting white. There is a disease/syndrome called Raynaud's, in which the tiny blood vessels, especially in hands and feet, have an extreme reaction to cold and instead of constricting a bit, as happens in other people, they constrict a lot, causing color changes in the skin. You can read more about Raynaud's here - keep in mind that some of the information in that article may sound alarming, but it also states that made notes is usually not a severe health risk. I have a friend who used to have Raynaud's back when she was very thin, she gained some weight, got healthier and it seemed to have helped her symptoms. Is your RA well controlled? If it isn't, that may affect these symptoms (I'm guessing here - just seems to make sense), so you may want to discuss the issue with your rheumatologist to see if there are treatment options that may help your health in general. You might also consider seeing a naturopathic doctor - I find that they are an excellent resource for building up your health in general and they can be found in your Yellow Pages. In general, Raynaud's is one of those things that's a pain in the rear, but can be managed - again, I recommend poking around on the Internet, reading blogs and sites of people who have the syndrome for tips. Even if your doctor doesn't agree you have this disease, some of the tips that people living away that have to scour it may help you anyway.