The Horseshoe Falls on the Canadian side looked equally cold and dull.
Sure, they look powerful and the severity of the winter is apparent. It's just not uplifting. There is no "eye candy" offered.
The next afternoon, the sky was clear and the sun lined up directly opposite the American Falls. Seen from the rim of the gorge with the sun directly behind me, it became writing with good light.
There is a lively S-curve traced from the top; it begins on the flat river above the drop and runs diagonally down the rainbow to the bottom where the largest boulder pulls you back to the left. -- Okay, it is really a Z path, but cut me some slack here. Okay?-- This was exciting. It was ice on fire, eh?
As I shifted location, I could place the rainbow where I wanted it to be. So, this scene was built by my action, not by accident.
At another location, the composition was equally interesting. Again I shifted laterally to put the color where I wanted.
Now, a majority of the people along the side of the gorge were taking photos with their phone. They captured none of this beauty, because the lens is such a very wide angle that from a distance, it cannot remove all the surrounding clutter and present a clear message. The simplest compact camera would have sufficed to tell the beauty of a rainbow in the waterfall. Snap shooters are making a big mistake abandoning their compact point and shoot camera in favor of the smartphone. They will get home and find the rainbow is missing.
Note: I used a mirrorless, the V2 Nikon Series 1, camera for the rainbow images. It is just one step above a point and shoot.