OK, I have changed the colors to a simple black text on a light grey background. This should work for all.
[I refuse to use a white background on aesthetic reasons. Like blue-jeans, it's simple so omnipresent that it crosses both borders of Boring and enters, almost, "irritating". Maybe that's just me. I haven't worn blue jeans (I have no other problems with other colors of jeans) for 40 years and I've never designed a site with a white background. Also a light grey background is more readable, for me and I think studies show it too.]
Btw, I agree that the wide margins are silly. But my HTML knowledge is limited, and I can't find the setting in the template which determines this...