private void loadThemeDefaultFiles() {
		defaults.clear();
		darkDefaults.clear();

		List<ResourceFile> themeDefaultFiles =
			Application.findFilesByExtensionInApplication(".theme.properties");

		for (ResourceFile resourceFile : themeDefaultFiles) {
			try {
				ThemePropertyFileReader reader = new ThemePropertyFileReader(resourceFile);
				defaults.load(reader.getDefaultValues());
				darkDefaults.load(reader.getDarkDefaultValues());
				processLookAndFeelSpecificValues(reader.getLookAndFeelSections());
			}
			catch (IOException e) {
				Msg.error(this,
					"Error reading theme properties file: " + resourceFile.getAbsolutePath(), e);
			}
		}
	}
Searches for all the theme.property files and loads them into either the standard
defaults (light) map or the dark defaults map.
Ghidra/Framework/Gui/src/main/java/generic/theme/PropertyFileThemeDefaults.java