It's weird that people dying is an effective way of moving knowledge forward. Intuitively, you'd think the longer people live the more they can learn and retain.
Although, the rainbow is discrete colors as opposed to a continuous gradient [2]. Hence how you can get a monochrome rainbow [1] (it only splits the colors present).
A "monochrome" rainbow is still a continuous decomposition of low temperature (warm) sunlight. A truly monochromatic "rainbow" requires a spectral light source.
Rainbow is a continuous gradient as opposed to discrete colors. The picture of the red rainbow is not a counterexample, it's just the light is red (a continuum of red) in the air during sunset/sunrise.
Do an image search for "rainbow drawing" and you will see what I'm talking about. People will draw a number of monochromatic segments with contour lines between them.
Although, the rainbow is discrete colors as opposed to a continuous gradient [2]. Hence how you can get a monochrome rainbow [1] (it only splits the colors present).
[1]: https://en.wikipedia.org/wiki/Rainbow#Monochrome_rainbow
[2]: https://en.wikipedia.org/wiki/Gradient