The theme setting in the new UI
The drop-down list in the new UI for different themes seems to be configured in such a way that just the coloured circle with colour is clickable but the name of the theme is not. I am not sure if it is designed in such a way deliberately.
But I think from a user's point of view, the text should be clickable as well since it is easy to just click the name rather than aiming for the small coloured circle.
User-friendly UI. Refer the attached image.