I want to give a border to all the buttons of settings that are enabled in my options menu.
Let's say that the demo mode is enabled, then the according "on" button should have an e.g. red border, while the "off" button hasn't got one. I don't care if the border is visible when you hover over the button (= the "highlighted" color is used) as long as the actual color change for highlighting/pressing the button still works.
So far I've only found the "Outline" effect but it only seems to work on the text component of a button, not the actual button itself. How do you do this in Unity (2017.3.1f1, preferably without using additional assets)?