Sorry sir but simple science. Rainbows reflect light from either sun or moon(sun's light, but still), and when reflected, it creates a multicolored strip, curved or straight.

Aside from being incorrectly termed as a rainbow, it is a nice, even series of undulating gradients with a blue tint. ^_^

I'll be honest though, looking at it too long does give me a bit of a headache due to the repeating pattern.

Some of your other work isn't too bad, just keep on improving and you'll go far.

Guys calm it. It's not a rainbow. It's a blue spectrum.

See what I did there? :3

Rainbows are not blue?! Everyone is trying to tell you dat!!

um rainbows arent blue ;P

This is not a rainbow. This only has 3 repetitive colors. A rainbow has 7.

Could you add the side textures :3

youknow.. rainbows are rainbows because they contain a certain amount of color so something blue cannot be a rainbow..