Serve dark/light login page in custom theme

Hi all;
I am looking for a way to serve a login page that will have a light or dark theme depending on a dynamic parameter I have.
currently I have a single realm with a custom theme where I will want to apply this. can this be dome with a single realm and client?
can I “take over” the redirect url and append something like &theme=dark and have keycloak serve a dark theme instead of the default light?
also, we have a whitelabeling option that boils down to the same problem. when the product server is in “white labeling” mode I need to remove all logos etc. so my custom login page I serve from keycloak should also be served without logos
I assume many people bump into this issue. can someone point me in the right direction?
thanks