Use in ~/.bashrc (sourced by each non-login shell):
red='\e[1;31m'
green='\e[1;32m'
yellow='\e[1;33m'
blue='\e[1;34m'
purple='\e[1;35m'
cyan='\e[1;36m'
white='\e[1;37m'
reset='\e[0m'
PS1=${green}${PS1}${reset}
Test if terminal supports italic text:
echo -e "\e[3m foo \e[23m"