ivicaivica The color of the Phone app during calls changes to one particular color that I do not like. Is there a way to change it?
I suspect it would be possible to clone the built-in dialer, change the colors, build an APK, install it, and then designate that as your dialer (Settings, Apps, Default apps, Phone app). In terms of the build system, while this would be wasteful, you could probably build an entire GrapheneOS and snatch the dialer APK -- that might be simpler than figuring out how to build just the dialer. Please note that I haven't tried this.
In theory you could then submit a patch either to Google's AOSP project or to GrapheneOS. In practice, though, Google has deprecated this app, and the GrapheneOS developers might not want to review and then maintain the patch (especially since the app has been deprecated). Unless, of course, you were to choose a color combination that the developers found extremely attractive... perhaps black & white, if you catch my drift...
Please note that I don't speak for the GrapheneOS project.