The yellowing you have is a Jaundice condition, but its source is not known. Jaundice is usually associated with the liver and will show up, as a rule, in the eyes first.
Another jaundice look alike is is carotenemia, which people get if they eat a very large amount of yellow vegetables or drink large quantities of vegetable juice. How this could show in you fingers i have no idea, but it may be a factor relating to the real problem.
Nerve damage i would not rule out, but maybe look else where. If it is just the left( i assume the fretting hand) then i would look along that whole line from the neck through the shoulder, upper arm, forearm, wrists and fingers.
As you have an arthritis condition, (there are many) it maybe a circulation problem(joint swelling restricting blood flow) and the lack of red blood cells causes the numbness and the yellowing, again the yellowing a sympathetic symptom from another seemingly unrelated problem with fingers, but related to blood.
I would get a second opinion or even a third if you think it nessesary. Also talk to arthritus help groups, and find out if there is any documented evidence related to the condition.
