Gray is commonly used to indicate uncertainty or ambiguity, as in "that's a gray area." (See my post, only partly tongue in cheek, on my own uncertainties.) It is also used to indicate gloom or despair, as in "gray skies."
The Wikipedia article on gray says that it is produced by mixing black and white. You won't find gray in rainbows, because it is a mixture.
Gray is also spelled grey, in British English.
There are six uses of the word, gray, in the Bible. All of them are in the Old Testament, and all of them refer to the hair of older persons. Gray is used to refer to older people now, as in "gray power."
The brain contains gray matter.
Grayscale images are images with shades of black and white. Black and white TVs are actually grayscale TVs.
Gandalf the wizard was called Gandalf the Grey in Tolkien's books. He became Gandalf the White later.
Eeyore, in Winnie-The-Pooh, was an old grey donkey.
I wish I had put this sort of thing in earlier, beginning with my post on red, but I attend a non-liturgical church (We have our rituals, but they aren't printed in the bulletin!) and it just didn't occur to me. Our younger daughter attends one, and she reminded me that, to liturgical churches, colors have significance in worship. I did a Google search, something like "blue green Episcopal," and the first hit was here. This church's web page had the following table on the significance of these colors in worship:
|BLUE - heavenly strength and faithfulness|
|WHITE - purity, innocence, and joy|
|GOLD - purity and splendor|
|RUBY or RED - the blood of life, sacrifice, and therefore, love|
|GREEN - Spring, hope, eternal life, and the Holy Trinity|
|YELLOW - the revealed truth, as the sun breaking through clouds after a storm|
|BROWN - the earthly, or the mundane|
|GRAY - the earthly, or mundane, and humility|
|PURPLE and VIOLET - royalty, or penance|
I thank the church, and my daughter, and I'm sorry I didn't think of this earlier.
Having been properly humbled (gray signifies that) I close this post. Thanks for reading.
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My wife found a typo in this post, which I have corrected, as of March 5th, 4:11 P. M. EST. Thanks to her, and I should be even more humble.