use spectrum.zsh instead of manual color assignment

plugins/upgrade/init.zsh

@@ -22,12 +22,12 @@ function upgrade_zsh() {
   zstyle -t ':omz:plugin:update-omz' auto-commit || local nocommit='--no-commit'
 
   if git pull $nocommit --strategy=recursive -X ours origin master; then
-    zstyle -t ':omz:plugin:upgrade' color && printf '\033[0;34m%s\033[0m\n'
+    zstyle -t ':omz:plugin:update-omz' color && printf "$FG[blue]"
     printf 'Hooray! oh-my-zsh is up-to-date :)'
     touch ~/.zsh-upgrade
   else
-    zstyle -t ':omz:plugin:upgrade' color && printf '\033[0;31m%s\033[0m\n'
     printf 'Oh no! There was an error upgrading oh-my-zsh :('
+    zstyle -t ':omz:plugin:update-omz' color && printf "$FG[red]"
   fi
 
   cd $current_path