Just seal it well or use Custom Building Products Prism grout. It requires no sealing. Not sure I would use bright white. I would match the grout to the lightest tile in the tile mix. Sometimes white is just too white. There are many shades of white!

By the way...looks nice. Congrats!

I would match the countertop, is it black? Or charcoal gray? Looks great!

I agree with Patterson. I would use a light tan or off-white, similar to lightest colored tile. The pattern is busy enough and if you use dark grout, it will make one's head spin.

I would head toward your second lightest tile color--those tan ones. Choosing a very dark or a very light grout will draw attention to the grout rather than the tiles.

Are you using acrylic or epoxy grout?

I'd choose that greyish tone from the tile, so the second lightest.