curses provides routines that manipulate color on color alphanumeric terminals. To use these routines start_color() must be called, usually right after initscr(). See curs_initscr(3CURSES). Colors are always used in pairs (referred to as color-pairs). A color-pair consists of a foreground color (for characters) and a background color (for the field on which the characters are displayed). A programmer initializes a color-pair with the routine init_pair. After it has been initialized, COLOR_PAIR(n), a macro defined in <curses.h>, can be used in the same ways other video attributes can be used. If a terminal is capable of redefining colors, the programmer can use the routine init_color() to change the definition of a color. The routines has_colors() and can_change_color() return TRUE or FALSE, depending on whether the terminal has color capabilities and whether the programmer can change the colors. The routine color_content() allows a programmer to identify the amounts of red, green, and blue components in an initialized color. The routine pair_content() allows a programmer to find out how a given color-pair is currently defined.

The start_color() routine requires no arguments. It must be called if the programmer wants to use colors, and before any other color manipulation routine is called. It is good practice to call this routine right after initscr(). start_color() initializes eight basic colors (black, red, green, yellow, blue, magenta, cyan, and white), and two global variables, COLORS and COLOR_PAIRS (respectively defining the maximum number of colors and color-pairs the terminal can support). It also restores the colors on the terminal to the values they had when the terminal was just turned on.

The init_pair() routine changes the definition of a color-pair. It takes three arguments: the number of the color-pair to be changed, the foreground color number, and the background color number. The value of the first argument must be between 1 and COLOR_PAIRS-1. The value of the second and third arguments must be between 0 and COLORS. If the color-pair was previously initialized, the screen is refreshed and all occurrences of that color-pair is changed to the new definition.

The init_color() routine changes the definition of a color. It takes four arguments: the number of the color to be changed followed by three RGB values (for the amounts of red, green, and blue components). The value of the first argument must be between 0 and COLORS. (See the section Colors for the default color index.) Each of the last three arguments must be a value between 0 and 1000. When init_color() is used, all occurrences of that color on the screen immediately change to the new definition.

The has_colors() routine requires no arguments. It returns TRUE if the terminal can manipulate colors; otherwise, it returns FALSE. This routine facilitates writing terminal-independent programs. For example, a programmer can use it to decide whether to use color or some other video attribute.

The can_change_color() routine requires no arguments. It returns TRUE if the terminal supports colors and can change their definitions; other, it returns FALSE. This routine facilitates writing terminal-independent programs.

The color_content() routine gives users a way to find the intensity of the red, green, and blue (RGB) components in a color. It requires four arguments: the color number, and three addresses of shorts for storing the information about the amounts of red, green, and blue components in the given color. The value of the first argument must be between 0 and COLORS. The values that are stored at the addresses pointed to by the last three arguments are between 0 (no component) and 1000 (maximum amount of component).

The pair_content() routine allows users to find out what colors a given color-pair consists of. It requires three arguments: the color-pair number, and two addresses of shorts for storing the foreground and the background color numbers. The value of the first argument must be between 1 and COLOR_PAIRS-1. The values that are stored at the addresses pointed to by the second and third arguments are between 0 and COLORS.

In <curses.h> the following macros are defined. These are the default colors. curses also assumes that COLOR_BLACK is the default background color for all terminals.

COLOR_BLACK
COLOR_RED
COLOR_GREEN
COLOR_YELLOW
COLOR_BLUE
COLOR_MAGENTA
COLOR_CYAN
COLOR_WHITE