Alternate color scheme for different categories

We have separate sections for some of our alternate publications within the main site. eg. Main site is international, however, there are separate subsections that are EU, India, Turkey etc. We have content that would be published in the main site that would also be located in EU, India or Turkey and would be called by category or tag - depending on how we move forward. We ultimately would like to have a different theme/color scheme/layout for each of these sections. Easy to do with just the main landing page. However, when you click on the article in EU for example, the template being used for the post ends up reverting back to the main site’s theme.

Is there a way to designate which theme layout is to be used based on where the reader is coming from?

Reader has clicked on: goes to main theme/template

BUT if Reader clicks on the same article but from: - can it keep the /europe/ theme while they are reading that article?