For coastal I think blue, and you already have some blue in your rug. With a dark counter, I'd go with a light blue tile, like this one Portmore Sky Bluein 4x4 or 3x8. That one's from Tilebar, so you can upload a picture and use their visualizer tool. (I'd try taking a picture with the lights on and the counters cleared, then upload into the visualizer.) That's just one idea, and if you can it would be great to visit local tile stores and pick up some samples.

I was thinking a light blue, too.

What @chicagoans picked out, would be perfect. Love the variation of shading.