Color models. The color of an object is generally described by its location in some color space or model. Most often, in computer displays, this model is RGB, or Red, Green, Blue. These three components of the color are each listed in values from 0 to 255 for 16-bit color displays, for over 1.6 million color combinations. For example, a saturated red would be (255, 0, 0) in RGB space, whereas a desaturated dark green might be (150, 220, 150). Each of these colors has a corresponding coordinate value in HLS (Hue, Lightness, Saturation) space. Hues in such a model are generally listed from 0 to 255, and Lightness and Saturation are some real number between 0 and 100. Printers refer to the CMYK (Cyan, Magenta, Yellow, Black) model, based on the light-absorbing qualities of ink on paper. Combining inks of these colors is the basic idea of four-color process printing.
Advanced color techniques. Displaying information with an emphasis on its divergence from the mean or from some other arbitrarily chosen attribute value can best be done by using a diverging two-hue color scheme. In this scheme, low values are indicated by a saturated, dark hue (for example, maroon), values around the mean are indicated by a desaturated gray tone, and values much higher than the mean are indicated by a saturated second hue (for example, royal blue). This gives the visual emphasis on the locations of the extremities of the data. Data on relative poverty and wealth would be appropriate to represent using this color scheme, since a viewer would likely be interested in both the poorest and wealthiest regions. Click to go an example of this color scheme.
A designer interested in emphasizing the relative amount of two qualities that differ in kind from one another would be wise to use a hue transition scheme. A display showing the party affiliation of the state congresses for all fifty states might use a bright red for a heavily Republican state congress, a purple (red-blue) for a 50-50% mix of party affiliation, and a bright blue for a heavily Democratic representation.
Opacity. One further dimension of color which is becoming more widely available in on-screen displays is a color’s opacity. Three-dimensional displays of time series data or atmospheric phenomena might take advantage of this characteristic of color by enabling a viewer "see through" a surface.