section Color Handling

While the curses library works with color pairs (reflecting the inability of some devices to set foreground and background colors independently), there are separate capabilities for setting these features:

To change the current foreground or background color on a Tek‐
tronix-type terminal, use setaf (set ANSI foreground) and setab
(set ANSI background) or setf (set foreground) and setb (set back‐
ground). These take one parameter, the color number. The SVr4
documentation describes only setaf/setab; the XPG4 draft says that
“If the terminal supports ANSI escape sequences to set background
and foreground, they should be coded as setaf and setab, respec‐
tively.
If the terminal supports other escape sequences to set background
and foreground, they should be coded as setf and setb, respec‐
tively. The vidputs and the refresh functions use the setaf and
setab capabilities if they are defined.

The setaf/setab and setf/setb capabilities take a single numeric argu‐
ment each. Argument values 0-7 of setaf/setab are portably defined as
follows (the middle column is the symbolic #define available in the
header for the curses or ncurses libraries). The terminal hardware is
free to map these as it likes, but the RGB values indicate normal loca‐
tions in color space.

Color       #define       Value       RGB
black     COLOR_BLACK       0     0, 0, 0
red       COLOR_RED         1     max,0,0
green     COLOR_GREEN       2     0,max,0
yellow    COLOR_YELLOW      3     max,max,0
blue      COLOR_BLUE        4     0,0,max
magenta   COLOR_MAGENTA     5     max,0,max
cyan      COLOR_CYAN        6     0,max,max
white     COLOR_WHITE       7     max,max,max

The argument values of setf/setb historically correspond to a different mapping, i.e.,

Color       #define       Value       RGB
black     COLOR_BLACK       0     0, 0, 0
blue      COLOR_BLUE        1     0,0,max
green     COLOR_GREEN       2     0,max,0
cyan      COLOR_CYAN        3     0,max,max
red       COLOR_RED         4     max,0,0
magenta   COLOR_MAGENTA     5     max,0,max
yellow    COLOR_YELLOW      6     max,max,0
white     COLOR_WHITE       7     max,max,max

It is important to not confuse the two sets of color capabilities; otherwise red/blue will be interchanged on the display.