Grey or gray is an achromatic or neutral color.

Complementary colors are defined to mix to grey, either additively or subtractively, and many color models place complements opposite each other in a color wheel. To produce grey in RGB displays, the R, G, and B primary light sources are combined in proportions equal to that of the white point. In four-color printing, greys are produced either by the black channel, or by an approximately equal combination of CMY primaries. Images which consist wholly of neutral colors are called monochrome, black-and-white or greyscale.

The first recorded use of grey as a color name in the English language was in AD 700.Grey is the British, Canadian, Australian, Irish, New Zealand and South African spelling, although gray remained in common usage in the UK until the second half of the 20th century.Gray is the preferred American spelling, although grey is an accepted variant.Gray became the preferred spelling in American English around 1825.

Most grey pigments have a cool or warm cast to them, as the human eye can detect even a minute amount of saturation.^{[citation needed]}Yellow, orange, and red create a "warm grey". Green, blue, and violet create a "cool grey". When there is no cast at all, it is referred to as "neutral grey", "achromatic grey" or simply "grey".

Version means a specific form or variation of something. It can refer to:

Libre ( /ˈliːbrə/) is a loan word in English borrowed from various Romance languages, including Spanish and French. As it does in those languages, "libre" in English denotes "the state of being free", as in "having freedom" or "liberty".

From the mid-1990s onward, libre became increasingly used to distinguish "free" as in freedom from "free" as in free of charge (the gratis versus libre distinction). For example, the distinction is made in the free/libre and open source software (FLOSS), free culture, open knowledge and libre knowledge communities. An adage of the free software movement that explains this difference reads:

In these contexts, libre encompasses the essential freedoms defined in the free software definition, and is used to describe works which may be used, modified, copied and shared without permission from the copyright holder. Examples of terms that include the adjective libre: libre software, FLOSS, libre knowledge and libre cultural works. Public copyright licenses that guarantee these freedoms ("libre licences") often require attribution for contributors and sometimes include copyleft terms that ensure these essential freedoms remain in future derivative works. Works that are in the public domain are also considered libre.^{[citation needed]}