What is the rationale for calling these "strong"? I don't think I've ever seen them referred to as anything other than "bright".
"Strong" was entirely made up by me. I didn't want to use "bold" because is may cause confusion with bold text. "Bright" is fine.
I think these two lines could be expressed as for k in ${color[(I)[39]?]}; do color[fg-${color[$k]}]=$k; done
LGTM