Detect color resolution of the terminal

color.sh

#!/bin/sh

detect_color_resolution() {
    # 24bit
    if [ "$COLORTERM" = "truecolor" ]
    then
        printf '%s\n' 24
        return
    elif [ "$COLORTERM" = "24bit" ]
    then
        printf '%s\n' 24
        return
    fi
    # 8bit
    case $TERM in
        *-256color)
            printf '%s\n' 8
            return
            ;;
    esac
    # lets ask tput, bleh!
    local TPUTCOL=$(tput colors)
    case $TPUTCOL in
        256)
            printf '%s\n' 8
            return
            ;;
        8)
            printf '%s\n' 3
            return
            ;;
        *)
            printf '%s\n' 0
            return
            ;;
    esac
}

printf '%s\n' $(detect_color_resolution)