Excessive Yellow When Top Coat is Applied: A small amount of yellowing is expected and should be quickly neutralized by adding a violet or black tint to the top coat. However, if you are experiencing a lot of yellows that will not neutralize, there are a few things to look for. First is an insufficient deposit of metal. The finish should be very bright before going to the top coat. A thinner metal deposit can cause a yellow finish. Second, this process should not be attempted if your shop’s humidity level is above 60%.