macOS Source List Icons

Hey ho,

I'm trying to create source list like those in the Finder and iTunes. I downloaded Apple's SourceView demo-program, and it's great.
I set the childrenDictionaries to use icons that I created.
The problem is that, the icons of the childrenDictionaries when pressed they don't change to a white-is tone.
How can I make it to change when pressed?


HeyBro

P.S.: Sorry if I'm being unclear, please ask if you don't understand something!

As you can see, the ContentView2 is selected but the gear icon didn't have change to a white gear like it does with all of the sidebar icons in Finder, Mail and iTunes