ROY.G.BIV stand for the colors of the rainbow that we learned in art class in grade school:
That worked for me until I started studying photography and working in a photo lab. The colors of light are a different thing almost entirely. This photo illustrated the actual colors of the rainbow diffracted through a crystal in my window.
At the bottom left, there’s your red, then yellow, green, cyan, and blue to the top right. The three primaries are red, green, blue. If you were to overlap the red and blue, you would get magenta. So, no matter how many colors you think you are seeing in the sky, this is what you are actually seeing.