Is indigo really a color in the rainbow?
Yes, Sean, it is. But it is a color that the human eye is not very
sensitive to so we do not see it very well. It's frequency is between
blue and violet, both of which we see better.
No. Although all the blues in a rainbow do contain some red, there is
no place in the rainbow where a deep enough blue combine with enough
red to make indigo. But isn't ROYGIV easier to pronounce than ROYGBV?
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Update: June 2012