How do I change the dock indicators color ?

the open app indicators in the dock are black, making them difficult to see most times since my dock background is gray.

would like to change the indicators to white, they would be much easier to see.

no 3rd party apps installed that can alter/customize the dock.

any suggestions on what to look for/change ? can i do this via a terminal command, or change a file inside the package called "Dock.app" (Library-->Core Services-->Dock.app)