@Override
	public List<DockingActionIf> getActions() {
		List<DockingActionIf> actions = new ArrayList<>();
		actions.add(new AbstractColorOverviewAction("Show Legend", getName(), overviewComponent,
			getHelpLocation()) {

			@Override
			public void actionPerformed(ActionContext context) {
				PluginTool tool = overviewComponent.getTool();
				tool.showDialog(getLegendDialog());
			}
		});
		return actions;
	}
Kick when the colors have been changed.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/overview/entropy/EntropyOverviewColorService.java