changing Presenter Notes font size, color, etc

So, I've been puzzled for the longest time how to change the Presenter Notes text / paragraph for all slides at one time.
I often import files from PPT and need to type notes during lectures. However, sometimes, the presenter notes text is white, and then I have to change each slide to black text as I move along the lecture.
Other times, I need to change the font type and line spacing.

Is there a way to change all presenter notes text/paragraph all at once?
If I select all slides, the option to change the Presenter Notes grays out.
And the option is not available if I select the master slides.
And, there is no option to 'make text the default' setting, as often enough this might be an expected menu item but I can't seem to see anything of similar nature.

I welcome all comments.
Regards. Radu