Once you’re done testing, verifying and checking it’s time to export your style. As I explained earlier, the theme is stored in the database and contains, among other things, the colors for the moderator and administrator user links in the Who’s Online box.
When a user adds a template and its associated themes, these values are loaded from the theme_info.cfg file into their own database so unless you write these changes to your theme_info.cfg file they will not be included. This is precisely what happens when you Export a style, all the database entries associated with it will be written to the theme_info.cfg file. Should phpBB fail to write to the file you can try changing the permissions for it and setting them to 777 (chmod 777). You can also download it and save/upload it manually.