Yes, it is possible to change element color using nested symbols like in the video below and also define own styles, but you can't change color for the element (ie. button) and the headline in one action. Another example - you have 10 master symbols with the same border-radius. When you need to change the radius size, you have to edit each master symbol manually. It would be nice if the value for the radius could be read from some "variable list".
My Project Variable List:
And the designer will be able to "pick" those variables in Sketch UI (color, size, dimension, checkbox, ...).
Later you can define a new "variable list" and override the default one.
Dark Variable List > My Project Variable List:
Video - https://youtu.be/gBdtToxlQFc?t=185