Change button color in ofxGUIextended

Hi,

I want to implement some kind of ‘dark mode’ in my menu that I am using. CUrrently I can change the background color of e.g. a group of parameters that has been added to my container. However, I have also added a single button into the container (not part of a group) and I cannot figure out how to change that background or fill color. Here’s a code snippet:

settingsContainer= gui.addContainer(“Container”, ofJson({{“height”, 16 },{“width”, 280}}));
settingsContainer->add(saveXml.set(“Save settings”), ofJson({{“type”, “fullsize”}, {“text-align”, “center”}}));

I’ve tried various background color or setfill color functions for the total container, but those do not seem to work (although they compile).

Any idea how to accomplish ‘button color change’?