[Lynne]

There is no way to do that in default vbulletin. I can't think of an easy way to change this. I suppose to could edit the footer template and manually write the style chooser to only output style 1, 2, 3 in some forums and then only 4 and 5 in other forums. But, then I think you would need a plugin to make sure that in those forums, they have selected one of those styles and I think that will get messy with the style cookie and could end up being bothersome to your users.

edit: actually, maybe just a plugin for those forums where if they had selected style 1 (light), then show them style 4 (light) when in the other forums. Or vice versa for dark. That would probably be the easiest way. Except, you'll have to modify some permissions to allow them to see style 4 or 5. Perhaps another plugin for that?