A cache tag is used to tell Drupal 'what is in the cache', so the cache can be invalidated once something in the cache is updated. This is mainly used for entities and configurations.
Cache contexts provide... context (duh), so the exact same set of tags (entities) can exist under multiple circumstances with a different cache. Examples for contexts are languages and themes, where the same set of entities need to be rendered differently.
Now I did find how to invalidate cache tags:
Cache tags are invalidated using cache_tags.invalidator:invalidateTags() (or, when you cannot inject the cache_tags.invalidator service: Cache::invalidateTags()), which accepts a set of cache tags (string).
But I cannot find how to invalidate cache contexts...
The reason for asking this is because I am in the process of converting the white label module to Drupal 8. (This module allows the site name, logo and color scheme to be overridden initially based on a url token, but a session variable for subsequent pages.) So I thought such a whitelabel token would make up for an excellent cache context. However (probably on very low frequency) the parameters (name, logo, etc) could change. Thus I should invalidate the cache context.
Can I invalidate cache contexts? Or are there other options? I have thought of using a combination of both tags and contexts, but I am afraid the amount of combination will go through the roof...