Hello.

I wanted to have a different colour for the per-match descriptions in 
the menu list, but I can't get it to work in all cases.

- start a clean shell with `zsh -f`

- execute:
  > zmodload zsh/complist
  > autoload -U compinit && compinit
  >
  > zstyle ':completion:*' list-separator "XX"
  > zstyle ':completion:*:default' list-colors '=XX*=31'
  >
  > _a () {
  >     _arguments \
  >       '(--first -f)'{--first,-f}'[first should be red]' \
  >       '--second[second should be red]'
  > }
  > compdef _a a

- try:
   - `a -<tab>`  WILL show color
   - `a --<tab>` will NOT show color

This doesn't just happen when using `_arguments`. Using `_describe` and 
those specific zstyle's also doesn't work.

Screenshots + more tests & examples can be found here:
https://gist.github.com/Orangenhain/c9ac6ea47f187589813b9887c300a897

Is that a bug? Am I using list-colors wrong?

Thanks.