You need to pick the quartz before the backsplash & paint color. Backsplash should be chosen once everything else is installed. What quartz have you looked at? I hate gray so would not suggest grays but you may like it. So you need to go to a showroom and look

I am redoing my kitchen as well. Going to have my cabinets painted warm white, but I will first decide on the quartz. Don't want the countertop and cabinet paint to clash. You want it to blend. Plus, I am really thinking of having the backsplash done in quartz as well. No grout lines and easier to clean.

We’ve just finished having our new cabinets installed, and they are painted SW Extra White. We have also order Cloe tile in white in the 5x5 format and will have the backsplash installed in 2 weeks. The quartz we chose is from MSI, and is called Blanca Statuarietto. I love the vein detail because it’s interesting looking to me without being busy.

Here’s a quick pic of the samples set up

Lighting is not finished, we still need to get our pendant lights up and possibly a solatube