Change CSS definition at runtime / overwrite template variables at Runtime

Hi folks,

we are working on a feature in our program which lets users define the look of their app (images, highlight colors) in a configuration during runtime.
Is there a way in Vaadin to directly overwrite the CSS Definitions which are generated?
Otherwise we would need to “post process” every component that is rendered to change the colors accordingly.

Or are there other suggestions how to approach that with Vaadin?