So, I had a betta almost two years ago who was the happiest, most docile fish ever. Until I held a beight blue highlighter (the felt uncapped end of the marker) up to his tank. He went absolutely nutso. Flared his gills, fanned his fins, the whole shebang. After he decided it wasnt going to hurt him in any way, he decided it was fun to chase it around the tank. I currently have a betta who is the angriest fish I have ever met. He will war dance at me, full flare, fanned fins, just for looking at him. And as for the coloring, I have quite a few colorful bettas (just your plain old run of the mill red and blue bettas -usually- don't cut it for me) and most of them have an asymetrical coloring, or basically their colors differ on different areas of their body. Also, lighting and angle will have a lot to do with it also. If you're concerned about the coloring of your fish at any time, we'd recommend a light source that will eliminate shadows and let you see the fish from different angles.
Your fish sounds like a spunky healthy fish to me.