Just thought I’d share this, it’s very interesting …
take a look at this site: https://www.jenoptik.de
and watch closely - the colors of many elements like text, overlays etc. change.
When the background colors in the top header bar change, it affects all other elements on the page. You have to stay on the page for about 30 seconds to see the effect. I wonder how they did this. Do you think that they are somehow dynamically loading a new CSS file where all color parameters are changed?