I think I just fixed the problem now. And it's still 50 lines :D

If you don't mind a shameless plug, I made this same mistake before and here's how I fixed it: https://github.com/kccqzy/Wordle-Assistant/blob/27d208248b7a...

Here is one way to fix it (but it will push you over 50 lines!)

    remaining="" output=""
    for ((i = 0; i < ${#actual}; i++)); do
        if [[ "${actual:$i:1}" != "${guess:$i:1}" ]]; then
            remaining+=${actual:$i:1}
        fi
    done
    for ((i = 0; i < ${#actual}; i++)); do
        if [[ "${actual:$i:1}" != "${guess:$i:1}" ]]; then
            if [[ "$remaining" == *"${guess:$i:1}"* ]]; then
                output+="\033[30;103m ${guess:$i:1} \033[0m"
                remaining=${remaining/"${guess:$i:1}"/}
            else
                output+="\033[30;107m ${guess:$i:1} \033[0m"
            fi
        else
            output+="\033[30;102m ${guess:$i:1} \033[0m"
        fi
    done
    printf "$output\n"

Explanation:

The variable `remaining` tracks the letters of `actual` that can contribute toward yellows.

Here's my straight javascript version https://github.com/rrmm/mastermind-word . But it isn't particularly source length efficient.

Please let us know when that is fixed and I’ll play this for sure!