Function: tty-color-define

Specify a tty color by its NAME, terminal INDEX and RGB values.
NAME is a string, INDEX is typically a small integer used to send to
the terminal driver a command to switch this color on, and RGB is a
list of 3 numbers that specify the intensity of red, green, and blue
components of the color.
If specified, each one of the RGB components must be a number between
0 and 65535. If RGB is omitted, the specified color will never be used
by `tty-color-translate' as an approximation to another color.
FRAME is the frame where the defined color should be used.
If FRAME is not specified or is nil, it defaults to the selected frame.