What is an ink that is a muted grey, red/red-black, blue/blue-black, or any strange/cool/sheening/shading ink, while with at least with a modicum of formality that will work well on school-grade paper? I really want a grey that looks like pencil lead but is still readable, but that is not a necessity. My current choices are diamine graphite and monteverde blue-black, but I have never had either so opinions of those inks would be very helpful.