I prefer matching grout. I'd rather tile be the focus of the wall than grout.

I like the matching grout in your images as well - makes the fireplace pop. Can you blend the grill as well and maybe the light switches?

Definitely matching.

I read your post about Heath mid-century white tile on your fireplace. I am installing it as a kitchen backsplash and have the same question, contrasting or complimentary grout? What did you decide? Can you remember what grout you used? I’d love to see pictures!
Thank you,
Hilary

We ended up using complimentary grout wanted the tile to sing, not the grout, because the variation in the tile is beautiful I cant remember the name or color of rhe grout off hand. Heath had a grout sampler at their showroom and i had my tile guy use that brand. i had him make a sample board with a couple of shades to pick the one we thought workd best.