Sunsets are beautiful to watch, but I think very difficult to paint. You just can't improve on something so beautiful. Our family recently spent several days on Captiva, Florida, where the sunsets are magnificent. People line the beaches just to see each evening's performance. It is reported that some see a bright green speck just before the sun sets, but unfortunately we did not see it.
http://www.dailypaintworks.com/fineart/diane-campion/501-captiva-sunset/290524