Quite simply, there are a sed of ANSI escape codes that can be interpreted by bash or other good shells that can allow for nice colourization of output.
However, caution must be exercized, as with the use of echo, the -e option must be utilizied to allow for them to work. printf has no problems with them otherwise.
#!/usr/bin/env bash
RED='\033[0;31m'
GREEN='\033[0;32m'
NO_COLOUR='\033[0m'
printf "${RED}printf RED\n"
printf "printf ${NO_COLOUR} reset\n\n"
echo -e "${GREEN}echo GREEN"
echo -e "echo ${NO_COLOUR} reset"
A simple set of colours are listed below:
Black 0;30 Dark Gray 1;30
Red 0;31 Light Red 1;31
Green 0;32 Light Green 1;32
Brown/Orange 0;33 Yellow 1;33
Blue 0;34 Light Blue 1;34
Purple 0;35 Light Purple 1;35
Cyan 0;36 Light Cyan 1;36
Light Gray 0;37 White 1;37
A more complete set of codes and colours can be found on this Wikipedia page.