Original

Photoshopped

If you take a look at the first image, it's relatively similar to the second image, except that the second image has a slightly visible rainbow. I made the rainbow with help from this site
It shows you a step by step procedure, with pictures, on how to add a rainbow to your image. It can also show you how to add a double rainbow, which is something I haven't yet done, but would love to learn, and this website will show me how!