iOS Question SYSTEM button color - can it be changed?

Yes:
for the background color: Button.Color = Colors.Black
and for the text color: Button.TintColor = Colors.White

Ah no, I meant the colors used by the system - so currently my active STYLE_SYSTEM buttons have blue text when they're active.
I specifically want to keep them as STYLE_SYSTEM buttons, but wondered if a theme could be changed or something - ie what dictates the colors used for SYSTEM elements?

I don't think that the user can change these colors in anyway. New versions of iOS can change it.