I would leave the backsplash as is (4" matching) and paint the walls the very lightest color in the countertop.

A change from the red will be very refreshing! Doesn't sound very original, but I think I'd find a very light beige from the granite.

I think I’d do a medium beige-brown, a cocoa color that blends with the granite in the kitchen and contrasts with the wainscoting in the dining room. If you do decide to use a backsplash, I’d wait until after I painted and then make a choice, not only for the color of the backsplash, but also because it actually might look nice without one.

Hmmm. That’s a good thought to match it to something in the granite. Curious to see what some other thoughts are on the backsplash. Phun may be right in thinking no backsplash, but I’m not sure. May need to paint first then go from there.

As an alternative for the backsplash, you might want to
consider an easy-to-install epoxy wall tiles that’s
less costly and time consuming....could be mosaic or lighter flush color with subtle dimensional features.
Sometimes the small details can really make a design. Check out a few ideas here https://www.houzz.com/projects/1262017/kitchen-backsplash