Spectral rainbows! My rainbow flags nearly always have an infrared stripe above and ultraviolet stripe below. When looking at real rainbows I often see a hazy extension of color fading off either side corresponding to these categories. If you focus you will see it, but cameras display it much better. These electromagnetic wavelengths are just as real as the typical visual spectrum and offer a more complete picture. In most designs they appear near-black or dark red and dark violet, but I have occasionally drawn them as lighter desaturated versions of red & violet.
The rainbow traditionally has 7 spectral colors - Red Orange Yellow Green Blue Indigo and Violet (ROYGBIV). Of these 3 are primary (red, yellow, blue), 3 are secondary (orange, green, violet), & 1 is tertiary (indigo). Neutral green divides the warm and cool colors.
12 striped rainbow (primary+secondary+tertiary colors)
An expanded 12 striped rainbow gives all tertiary colors equal representation including one color that is not found in the electromagnetic spectrum (EMS) and is only seen by mixing light frequencies - Magenta. Since magenta isn’t part of the EMS it can go on either end of the rainbow.
The 12 colors are: Magenta, Red, Vermilion, Orange, Amber, Yellow, Lime, Green, Cyan, Blue, Indigo & Violet.
If we add IR & UV we get the full spectrum rainbow below.
I moved magenta to the bottom here so green remains near the middle for visual balance. 14 stripes is quite a lot, but makes for a lovely color gradient.
Remember to expand your rainbows. There is always more than meets the eye. 🌈