Raynaud’s occurs when fingers (and sometimes toes) mysteriously turn red, white, and/or blue, due to spasm of arteries. Episodes usually last 15-30 minutes. They can be triggered by the cold or stress, but can happen for seemingly no reason. It’s not really a disease, although it may sometimes be associated with many rheumatologic diseases. These include Lupus, scleroderma, Sjögren’s Syndrome, and more.
For most people, the symptom is simply curious. But if it’s overly bothersome or painful, there are treatments which may control it.