Yellow.

A primary color, yellow is also one of the most widely used colors on a palette. Because it can be used to create several different colors--orange when mixed with red, green when mixed with blue and so on--it's nearly as versatile as white or black. Yellow's complementary color is purple/violet.

On the word "yellow", per wikipedia:

"The word yellow comes from the Old English geolu, or geolwe which derived from the Proto-Germanic word gelwaz. The oldest known use of this word in English is in the Old English poem Beowulf, in a description of a shield made of wood from a yew tree."

Yellow is a warm color, though it is often used to evoke a sense of warning (along with the colors electric green or red in some instances), even in nature. Traditionally it has also been used in the form of a yellow ribbon to welcome military men and women home, contrary to its slang use to mean someone cowardly. It is also a color representing peace in India and courage in Japan. In parts of Europe it can be used to represent sadness, or love.

In spite of all the uses for yellow, it being a bright, warm color is what makes it stand out most. Adding this color to a generally neutral palatte of browns, grays and black changes it dramatically, even drawing attention away from the other colors in some cases.

British alternative rock band Coldplay used the color yellow to “paint” the song below:

Yellow by Coldplay