Below you can find bash codes which you can use with man pages or while reading log files:

'\e[0;30m' # Black - Regular
'\e[0;31m' # Red
'\e[0;32m' # Green
'\e[0;33m' # Yellow
'\e[0;34m' # Blue
'\e[0;35m' # Purple
'\e[0;36m' # Cyan
'\e[0;37m' # White

'\e[1;30m' # Black - Bold
'\e[1;31m' # Red
'\e[1;32m' # Green
'\e[1;33m' # Yellow
'\e[1;34m' # Blue
'\e[1;35m' # Purple
'\e[1;36m' # Cyan
'\e[1;37m' # White

'\e[4;30m' # Black - Underline
'\e[4;31m' # Red
'\e[4;32m' # Green
'\e[4;33m' # Yellow
'\e[4;34m' # Blue
'\e[4;35m' # Purple
'\e[4;36m' # Cyan
'\e[4;37m' # White

'\e[40m'   # Black - Background
'\e[41m'   # Red
'\e[42m'   # Green
'\e[43m'   # Yellow
'\e[44m'   # Blue
'\e[45m'   # Purple
'\e[46m'   # Cyan
'\e[47m'   # White
'\e[0m'    # Text Reset

If you are using less application for viewing man pages you can add below variables to your .bashrc file. After that reload .bashrc variables with command: source /home/user/.bashrc and you will see colored man pages.

export LESS_TERMCAP_mb=$'\E[01;31m'
export LESS_TERMCAP_md=$'\E[01;31m'
export LESS_TERMCAP_me=$'\E[0m'
export LESS_TERMCAP_se=$'\E[0m'
export LESS_TERMCAP_so=$'\E[01;44;33m'
export LESS_TERMCAP_ue=$'\E[0m'
export LESS_TERMCAP_us=$'\E[01;32m'

For log files use perl syntax with your combined regex:

 tail -f  /var/log/mail.log | perl -pe 's/(fatal|error|panic|success)/\e[1;31m$&\e[0m/g'

Last colored trick. Use grep command with —color switch.