ROYGBV

https://www.free-power-point-templates.com/articles/how-to-make-a-rainbow-background-as-a-powerpoint-template/

#ff0000 Red
#ffa500 Orange
#ffff00 Yellow
#008000 Green
#0000ff Blue
#4b0082 Indigo (purple)
#ee82ee Violet (pink-ish)

#000000 Black
#ffffff White