I am not sure if I understood your question correctly. Gold does not dis color and definitely not due to customer’s careless handling.
Any unhappy customer is bound to create an unpleasant situation inside the store, especially if there are other customers. It is better to take the unhappy customer away from the main area into a room where she can be heard in full to determine how to solve the problem. The objective is not to finger point “careless handling” of the customer but to suggest that as a modern retailer, you will work a suitable situation to both the parties.
If the complaint is genuine, then it is better to accept the mistake and help in customer recovery. It is important to know that an unhappy customer will never return.