Hey! I'm super late and you most likely already figured it out by name but in case you didn't, to change it from light mode to dark mode all you need to do is go to Pause Menu > Options > Procedural Objects {version #} > Click the 'Use UI Night mode' option.

I do not know if you need to reload or not but if you click the option and see no changes, then a reload wouldn't hurt anything but your time lol.