Today's color of the rainbow is indigo. Weird color, sometimes described as a deep-purplish blue. Hmmm, it's actually kinda being dropped as a color of the rainbow, but I did manage to find this song!
By golly, I learned the colors by the acronym ROY G BIV (red orange yellow green blue indigo violet)
Duke Ellington, 1930 First covered by Ella Fitzgerald
You ain't been blue; no, no, no.
You ain't been blue,
Till you've had that mood indigo.
That feelin' goes stealin' down to my shoes
While I sit and sigh, "Go 'long blues".
(As his small boat scudded before a brisk breeze under a sapphire sky dappled with cerulean clouds with indigo bases, through cobalt seas that deepened to navy nearer the boat and faded to azure at the horizon, Buck wondered why he was feeling so blue.)
Always get that mood indigo,
Since my baby said goodbye.
In the evenin' when lights are low,
I'm so lonesome I could cry.
'Cause there's nobody who cares about me,
I'm just a soul who's
bluer than blue can be.
When I get that mood indigo,
I could lay me down and die.
Tomorrow purple ('cuz violet is harder to find)