My current problem is that I would like to give a preview of what the lights are displaying at a given moment so that I can better prepare fading effects in the beginning of a UDP Stream.

Solution
A new API command that returns the same kind of object as the websocket live stream would, but just once. For example /state/currCol or something else. In order to not further gunk up the /json/state message which can already be quite sizeable it might also be a good idea to leave it out of the state object.

Alternatives I have considered
The only solution I can find to get all current colors is to enable the live stream in a Websocket (so to send {"lv":true}), wait for a single frame and then disable the stream again. This is not an elegant solution.