I would like to see a list of pages where a particular style is used so I can either delete/modify it.
You can see a list of selectors not used on a page using external tools, there is no way for drupal itself to create the list for you however.
You can find some suggestions here: https://stackoverflow.com/questions/33242/how-can-i-find-unused-images-and-css-styles-in-a-website I personally use the chrome developer tools as described in the above link.
I can say that this is not possible.
A particular style is applied on either an id, class or an element. In Drupal, a page is generated by lots of different mechanisms including templates, modules, blocks, etc... So there is no easy way to track a particular id or class and find exactly in which pages does it exist.