How do I tell the freshness of raw chicken?
The yellow color could be just a sign of what it was fed. According to the USDA:


  THE COLOR OF POULTRY
  
  
  What is the usual color of raw poultry?
  Raw poultry can vary from a bluish-white to yellow. All of these colors are normal and are a direct result of breed, exercise, age, and/or diet. Younger poultry has less fat under the skin, which can cause the bluish cast, and the yellow skin could be a result of marigolds in the feed.
  


You could have an older chicken that had marigolds in what it was fed.

On the flip side, I was always taught that if any meat smells bad, it isn't good to eat. If it was my chicken in the kitchen, I would take it back to the store or just throw it out.

If you are still debating on if it is good to eat, you could always take it back to the store where you purchased it, or contact the USDA Poultry Hotline.