Poor indigo. You can’t spell “Roy G. Biv” without indigo, but no one ever remembers indigo.
There’s a specific reason for that omission!
The 7 color rainbow represents the perfection of God, seven days of creation - 7 colors = God’s rainbow.
The 6 color rainbow represents the autonomy of man. 6 is the “number of man”. It’s a subtle but purposeful middle finger to God to use a 6 color rainbow.
I know.
Maybe we should have a telethon or something...