Easily apply templates to your category archive pages and posts with this plugin.
Valid templates are files placed your theme folder with the following code at the beginning of them:
For Post Templates: Template Name: Blog Template
For Archive Templates: Archive Template: Blog Template
Through this plugin’s options panel, you can choose which templates are applied to categories and posts. Even choose their priority over one another. You can even apply a template to an individual post. 
Please <a href="http://aarongloege.com/blog/web-development/wordpress/plugins/wordpress-plugin-category-templates/#respond" rel="nofollow ugc">report any bugs</a> you come across.
Enjoy!

Category Templates

Give your categories and posts their own individual templates.

shazdeh

Just like the way you can create custom page templates, this plugin enables you to build category archive templates by adding this bit to the top of your file:
<pre><code><?php
/**
 * Category Template: Grid
 */
?>
</code></pre>
and when you’re adding or editing categories, you can choose the desired template file.
This plugin is maintained solely for backward compatibility. Try the new <a href="https://wordpress.org/plugins/custom-taxonomy-templates/" rel="ugc">Custom Taxonomy Templates</a> instead, it supports all taxonomies and also uses the new term meta feature in WP 4.4.

Custom Category Templates

Define custom templates for category views.

Category Templates vs Custom Category Templates