mint-y-dark desktop theme not visible which app is active

[zboraon]

In mint-y-dark desktop theme, if you open multiple instances of an application, then it is not possible to decide from the panel which one is active. If a contrast is given to the selected app mark, it would be much better.

[David2095]

https://github.com/David2095/mint-themes/releases

I only modified gtk-3.0/gtk.css and cinnamon.css. Mostly only colors.
The first two lines of gtk.css are color definitions. So it is easily adaptable from "Aqua" to another. And then replace them two colors in cinnamon.css too.