if [ "$TERM" = "linux" ]; then
    echo -en "\e]P0232323" #black
    echo -en "\e]P82B2B2B" #darkgrey
    echo -en "\e]P1D75F5F" #darkred
    echo -en "\e]P9E33636" #red
    echo -en "\e]P287AF5F" #darkgreen
    echo -en "\e]PA98E34D" #green
    echo -en "\e]P3D7AF87" #brown
    echo -en "\e]PBFFD75F" #yellow
    echo -en "\e]P48787AF" #darkblue
    echo -en "\e]PC7373C9" #blue
    echo -en "\e]P5BD53A5" #darkmagenta
    echo -en "\e]PDD633B2" #magenta
    echo -en "\e]P65FAFAF" #darkcyan
    echo -en "\e]PE44C9C9" #cyan
    echo -en "\e]P7E5E5E5" #lightgrey
    echo -en "\e]PFFFFFFF" #white
    clear #for background artifacting
fi

Source: https://askubuntu.com/questions/147462/how-can-i-change-the-tty-colors#153493