If you can find a honed or sueded grey granite you like it could play well / flow with the marble in the kitchen. Virginia Mist is one that you could call around and ask to see if they have slabs available. It would give the laundry a more casual feel. Definitely don’t do a quartz unless it’s a solid - but since you’re already in the real stone world with kitchen I’d continue along that vein.

You have what my family calls a ”utility room”. A gem! The counters will receive a lot of use, maybe washing off muddy shoes, and you say tinker space, with perhaps glues, Goof-Off, solvents, etc. Consider countertops that will stand up to it. Like Corian or even Formica.