Greetings.
This seems to be what we term as intestinal flu or viral gastroenteritis. This is a self limiting disorder as it resolves on its own in 3-4 days. If your severity of the abdominal pain is gradually decreasing, and your are getting continually better, you should not be concerned. Your belly button color change without any irritation or pain is of no consequence and is not symptom of any disease. Probably any pressure either by clothing or button might have caused that. Drinking plenty of liquids and taking fibers will further assist to overcome the problem
Hope this helps you. Your follow up questions are welcome.
Dr. Arun
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