Chromaticity is an objective specification of the quality of a color regardless of its luminance, that is, as determined by its hue and colorfulness (or saturation, chroma, intensity, or excitation purity).

In color science, the white point of an illuminant or of a display is a neutral reference characterized by a chromaticity; for example, the white point of an sRGB display is an x,y chromaticity of [0.3127,0.3290]. All other chromaticities may be defined in relation to this reference using polar coordinates. The hue is the angular component, and the purity is the radial component, normalized by the maximum radius for that hue.

Purity is roughly equivalent to the term "saturation" in the HSV color model. The property "hue" is as used in general color theory and in specific color models such as HSV or HSL, though it is more perceptually uniform in color models such as Munsell, CIELAB or CIECAM02.

Some color spaces separate the three dimensions of color into one luminance dimension and a pair of chromaticity dimensions. For example, the chromaticity coordinates are a* and b* in CIELAB, u and v in CIELUV, x and y in xyY space, etc. These pairs define chromaticity vectors in a rectangular 2-space, unlike the polar coordinates of hue angle and saturation that are used in HSV color space.

Tony MacAlpine (born August 29, 1960) is an American musician and composer. In a career spanning more than two decades and eleven studio albums, he is best known as an instrumental solo guitarist, although he has worked with many different bands and musicians in guest appearances and collaborations.

Having started playing piano at the age of five and guitar at twelve, MacAlpine studied classical music for a number of years at the Springfield Conservatory of Music in Massachusetts, as well as various music programs at the University of Hartford in Connecticut. One of his musical influences is Frédéric Chopin, to whom he pays homage in his interpretations of the latter's études, which are featured on the majority of his studio albums.

Together with his first studio releases, Edge of Insanity (1985) and Maximum Security (1987), he had a prominent role on other works during the popular shred era, including keyboard duties on the debut albums of fellow guitarists Vinnie Moore and Joey Tafolla, on Mind's Eye (1986) and Out of the Sun (1987) respectively. Soon after his own debut, he played guitar in a heavy metal supergroup named M.A.R.S. (an acronym for MacAlpine/Aldridge/Rock/Sarzo), which resulted in the album Project: Driver (1986).