Reader mode in Safari (at least on iOS) renders this nicely for me automagically, and turns the grey to a nice black. For the desktop I was going to recommend

Reader mode in Safari (at least on iOS) renders this nicely for me automagically, and turns the grey to a nice black. For the desktop I was going to recommend Distill Mode in Chrome (add --enable-dom-distiller to the command line/launcher, then it's available from the vertical "..." menu top right) but it didn't behave the way I remembered it. You get a nicely formatted page with all (or at least most) of the extraneous crap filtered out, but the grey remains. Internet Explorer supposedly has a Reading Mode too, but I can't find it on my desktop.