Single.php?

I have three category pages (category-5.php, category-6.php, and category-7.php) and I want each one to have a different look if a single post is viewed, is it a simple as creating 3 copies of single.php? like single-category-5.php, single-category-6.php, and single-category-7.php?)
Thanks

Here’s a list of the accepted templates: http://codex.wordpress.org/Theme_Development#Template_Files_List

And templates for categories: http://codex.wordpress.org/Category_Templates#What_Template_File_is_Used.3F

And a overview of the hierarchy of templates: http://codex.wordpress.org/Template_Hierarchy#Visual_Overview

I’m not sure if that’s quite what you’re looking for.

I am just going through some tutorials this past week and I don’t think that’s how you woudl do this. i am very new to php and WP template design but from what I understand you would have one single.php post, that perhaps would call a diffrent style depending on the class /catogory called.