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# 9.2 Color Functions

A color is represented by a CLX color object, in which each of the red, green, and blue values is specified by an rgb-val -- a floating point number between 0.0 and 1.0. (see paragraph 1.6, Data Types). The value 0.0 represents the minimum intensity, while 1.0 represents the maximum intensity. CLX automatically converts rgb-val values into 16-bit integers when sending colors to an X server. The X server, in turn, scales 16-bit color values to match the actual intensity range supported by the screen.

Colors used on :gray-scale screens must have the same value for each of red, green, and blue. Only one of these values is used by screen hardware to determine intensity; however, CLX does not define which of red, green, or blue is actually used.

The following paragraphs describe the CLX functions used to create, access, and modify colors.

make-color | &key (:blue 1.0) (:green 1.0) (:red 1.0) &allow-other-keys | Function

| :blue, :green, :red rgb-val values that specify the saturation for each primary. Creates, initializes, and returns a new color object with the specified values for red, green, and blue. color Type color.

color-blue | color | Function

| color A color object. Returns and (with setf) sets the value for blue in the color. blue-intensity Type rgb-val.

color-green | color | Function

| color A color object. Returns and (with setf) sets the value for green in the color. green-intensity Type rgb-val.

color-p | color | Function

| Returns non-nil if the argument is a color object and nil otherwise. color-p Type boolean.

color-red | color | Function

| color A color object. Returns and (with setf) sets the value for red in the color. red-intensity Type rgb-val.

color-rgb | color | Function

| color A color object. Returns the values for red, green, and blue in the color. red, green, blue Type rgb-val.

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