From NPR:
There are a lot of fascinating details hiding below the surface in the world of color. For instance, scientists once thought the average color of the entire universe was turquoise — until they recalculated and realized it was beige. In Japan, you wait at a stoplight until it turns from red to blue, even though it's the same green color as American stoplights. And in World War II, the British painted a whole flotilla of warships pinkish-purple so they'd blend in with the sky at dusk and confuse the Germans. That's right — pink warships. Design writer Jude Stewart's new book, Roy G. Biv, is full of facts like these. She tells NPR's Rachel Martin about the relationship between language and color, and what it's like to live with synesthesia.
…”Roy g biv” is a mnemonic that helps you remember the order of the colors of the rainbow. So it's red, orange, yellow, green, blue, indigo and violet.
On the surprisingly universal relationship between language and color
In 1969 these two linguists, Brent Berlin and Paul Kay, did a survey of 20 different languages that were completely unrelated to each other. And they found that as languages develop differing names for colors, those names always enter the language in the same order. So that order is black, white, red, green and yellow, blue, and then brown. So, if they're going to have only three words for colors, those words will almost always be black, white and red.
More here.