Same as "Page style". They don't need to do anything. It's just that they can set a different color for the active state for each swatch.
When you use the default theme but override the active or focus style, you are not only affected by this change but also (even more) by the fact that we use completely different selectors in the theme CSS. That is covered by the next section. I think it goes too far to show examples of how to override each part of the theme CSS.