Add unique class to each tag in the_tags

As far as I know, you’d have to hack the core and modify the_tags to do it one by one.

Instead, you should use get_the_tags as it does not display the tags, but just returns them for you to use and manipulate. See here http://codex.wordpress.org/Template_Tags/get_the_tags

The trick is to have each tag in a span with a class of the tag name, then you just need to create a new css class for every tag name with the styling you want.