I didn't know it, but I found something here:

http://www.tuxarena.com/2012/04/tutorial-colored-man-pages-how-it-works/

Instructions from the above link:

Edit your .bashrc file and add the following lines:

export LESS_TERMCAP_mb=$(printf 'e[01;31m') # enter blinking mode - red

export LESS_TERMCAP_md=$(printf 'e[01;35m') # enter double-bright mode - bold, magenta

export LESS_TERMCAP_me=$(printf 'e[0m') # turn off all appearance modes (mb, md, so, us)

export LESS_TERMCAP_se=$(printf 'e[0m') # leave standout mode    

export LESS_TERMCAP_so=$(printf 'e[01;33m') # enter standout mode - yellow

export LESS_TERMCAP_ue=$(printf 'e[0m') # leave underline mode

export LESS_TERMCAP_us=$(printf 'e[04;36m') # enter underline mode - cyan

Next, start a new terminal session or enter the command source ~./bashrc in your current terminal.