Not a big rainbow but just look at the color and pattern on this

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101 Brilliant Color Combinations

How to crochet with variegated and self striping yarn - Dora Does

I saw a rainbow today that appeared to have extra line/s beyond

100+ Patterns To Draw: Cool and Inspiring Patterns

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EarthSky Iridescent clouds have rainbow colors

Red-Green & Blue-Yellow: The Stunning Colors You Can't See

It's not a rainbow (it's better)

The Psychology of Color in Design, by Crezam