Is there a tool with compares the applied style of all elements within a parent element on diffrent URLS?

I'd like to do automated testing for some pages. For example I'd like to compare the styling of two pages. So if any changes have been made in your project a tool which compares the styles of two URLs (for example test server URL with new changes and testserver URL with default styles) would be awesome. If there are some big changes like merging different stylesheets to a new one to boost performance (prevent too many requests) a test if the computed styles match the old approved one would be very useful.

I already did some research an there are some tools for visual regression testing but they seemed not very useful. There are also some web scraping tools but none of them would fulfil my needs. Is there already some online tool, browser extension or testing plugin (on phantomjs base for grunt for example) that could do that available?

And would it be possible to select an element and get all styles for the child elements of it. And is it even possible to filter the source of the styles like in Chrome Developer tools (detect from which stylesheet or if inline style or from within a style tag) and filter only for the applied styles, not the overwritten ones etc.?