A color defines both the physical color of an element on the screen or in a plot as well as the transparency of that element. For example, a red color with full opacity will always draw a red element. However, one with half transparency will blend the color "below" it with red using half of each. The transparency is selected by the real number A which ranges from zero (fully transparent) to one (fully opaque). If the A key is not specified, it is assumed to be one for full opacity.

Color definitions also include the color model used to define the actual color. By default, this is the standard RGB (red, green, and blue) channels used with most computer graphics. While the alpha or transparency is common to all color models, the specific channels used depend on the one selected.

The color model in use is selected by the enumeration value Model:

RGB

The default color model consisting of channels for the red, green, and blue components of the color.

R

The real number of the red channel. This ranges from zero (none) to one (maximum).

G

The real number of the green channel. This ranges from zero (none) to one (maximum).

B

The real number of the blue channel. This ranges from zero (none) to one (maximum).

HSV

A color model that specifies the hue, saturation, and value of the color.

H

The real number of the color hue. This ranges from zero to one, specifying the spectrum of the color.

S

The real number of the color saturation. This ranges from zero to one, specifying how close to white the hue is.

V

The real number of the color value. This ranges from zero to one, determining how bright the color is.

HSL

A color model that specifies the hue, saturation, and lightness of the color.

H

The real number of the color hue. This ranges from zero to one, specifying the spectrum of the color.

S

The real number of the color saturation. This ranges from zero to one, specifying how close to white the hue is.

L

The real number of the color value. This ranges from zero to one, determining the color whiteness. Pure colors have a lightness of 0.5, with white at one and black at zero.

CMYK

A color model that specifies the cyan, magenta, yellow, and black components of the color. This color model corresponds to various print color specifications.

C

The real number of the cyan channel. This ranges from zero (none) to one (maximum).

M

The real number of the magenta channel. This ranges from zero (none) to one (maximum).

Y

The real number of the yellow channel. This ranges from zero (none) to one (maximum).

K

The real number of the black channel. This ranges from zero (none) to one (maximum).

Red
/R,1.0
Yellow with 25% transparenecy.
/Model,"RGB"
/R,1.0
/G,1.0
/A,0.25
Green in HSV
/Model,"HSV"
/H,0.47
/S,1.0
/V,1.0
Gray and pale red in HSL
/Model,"HSL"
/H,0.0
/S,0.2
/L,0.8
Dark blue in CMYK
/Model,"CMYK"
/C,1.0
/M,1.0
/Y,0.0
/K,0.5