colors.sh

#!/bin/bash
set -e
# ANSI color table that relates to RGB (NOT true RGB)
# Written by: Robert J.

#        _/  _/    _/  _/                            _/
#     _/_/_/_/_/  _/  _/_/_/      _/_/_/    _/_/_/  _/_/_/
#      _/  _/    _/  _/    _/  _/    _/  _/_/      _/    _/
#   _/_/_/_/_/      _/    _/  _/    _/      _/_/  _/    _/
#    _/  _/   _/   _/_/_/      _/_/_/  _/_/_/    _/    _/

#######################################
### Main Functions ####################
#######################################

main_function(){
    [[ $1 == "--grey" || $1 == "--gray" ]] &&
        greydisptable;

    [[ $1 == "--table" ]] &&
        disptable;

   [[ $1 == "--full-table" ]] &&
        predisptable &&
            disptable &&
                printf "\n" &&
                    greydisptable

    helpcheck "$@";

    die "" 0;
};

#######################################
### Generic Functions #################
#######################################

helpcheck(){
    for arg in "$@"; do
        [[ "$arg" == "--help" || "$arg" == "-h" ]] &&
            disphelp;
            die "" 0 --nosep
    done

    if [[ -z "${1}" ]]; then
        disphelp &&
            die "Invalid Syntax" 1;
    else
        return 0;
    fi

};

disphelp(){
    print "Command Documentation" green --nosep
    print "Usage Examples:" yellow;
        printf "\t%s --help | -h     \n\t# Displays this table for reference\n\n" "${0##*/}"
        printf "\t%s --table         \n\t# Outputs table of 216 escaped colors with approx RGB\n\n" "${0##*/}"
        printf "\t%s --full-table    \n\t# Outputs all 255 colors\n\n" "${0##*/}"
        printf "\t%s --grey | --gray \n\t# Outputs greyscale color codes\n" "${0##*/}"

    print "Options:" yellow;
        printf "\t--help | -h     \t# Displays this table for reference\n"
        printf "\t--table         \t# Outputs table of 216 escaped colors with approx RGB\n"
        printf "\t--full-table    \t# Outputs all 255 colors\n"
        printf "\t--grey | --gray \t# Outputs greyscale color codes\n"

}

print(){
    # opted against $_ and $! for this usage
    last="${!#}"
    output="$1";
    size="${#output}";

    # Colors calculated from ansi-color script
    ##########################################
    case "$2" in
        red)
            color="196"
            ;;
        orange)
            color="202"
            ;;
        yellow)
            color="226"
            ;;
        green)
            color="46"
            ;;
        blue)
            color="27"
            ;;
        indigo)
            color="21"
            ;;
        violet)
            color="54"
            ;;
        grey)
            color="8"
            ;;
        *)
            color="8"
            ;;
    esac

    printf -v sep "%${size}s" "-";

    [[ "$last" == "--nosep" ]] && {
        printf "\e[38;5;%dm%s\e[0m\n" "$color" "$output";
        return 0;
    };

    printf "\n\e[38;5;%dm%s\e[0m\n%s\n" "$color" "$output" "${sep// /-}";

};

die(){
    message="${1}"
    exit_code="${2}"

    [[ -z "$exit_code" ]] && {
        exit_code=1;
    };

    # determine if exit code is an integer
    [[ -z ${exit_code//[0-9]/} ]] || {
        print "Invalid exit code specified in script: $exit_code\n" yellow --nosep
        exit_code=255;
    };

    [[ "$exit_code" -gt 0 ]] && {
        print "Error Encountered:" "red";
    };

    print "${message}" "yellow" "--nosep";
    exit "$exit_code";
};

#######################################
### Program Specific Functions ########
#######################################

disptable(){
    print "More complex color codes:"

    # Set variables to 0
    r=0
    g=0
    b=0

    # Initiate while loop
    while : ;
    do

        # Starting with red (RGB)
        for ((r=0;r<6;r++));
        do

            # Perform color calculations
            color=$((16+36*r+6*g+b));

            # Print Color with RGB structure tabbing at the completion
            printf "\e[38;5;%dm%s,%s,%s;\e[0m color code: %s \t" "$color" "$r" "$g" "$b"  "$color";
        done;

        # Increase blue by one increment
        ((b++)) && {

            # Reset blue to zero if it equals 6
            [[ $b = 6 ]] && b=0 && {

                # Increase green by one increment until it equals 6 at which point, break the while loop
                ((g++)) && [[ $g = 6 ]] && break;
            }
        }

        # perform a line return after the first set of red is completed
        printf "\n"

    done;
}

predisptable(){
    print "Simple color codes:"

    for c in {1..15}; do
        printf "\e[38;5;%dmx,x,x;\e[0m color code: %s\n" "$c" "$c";
    done
}

greydisptable(){
    print "Greyscale color codes:"

    for c in {232..255}; do
        printf "\e[38;5;%dmx,x,x;\e[0m color code: %s\n" "$c" "$c";
    done
}

#######################################
### Execution #########################
#######################################

main_function "$@"

This is just a simple bash script that I whipped up to help determine the perfect ANSI Color code for other scripts: