It's a common confusion about terminal colours... Actually we have this:
- plain ascii
- ansi escape codes (16 colour codes with bold/italic and background)
- 256 colour palette (216 colours + 16 ansi + 24 gray) (colors are 24bit)
- 24bit true colour ("888" colours (aka 16 milion))
printf "\x1b[${bg};2;${red};${green};${blue}m\n"