Either mint green or grey/white would work well. I’d definitely recommend not to have white grout. We have ‘gun metal’ grout in both our bathrooms and it never looks grubby. Topps have a huge range of grouts.
Have a look at some from here www.firedearth.com/tiles - we have some lovely mint green glass mosaic ones from here as a strip of tiles. So you can do a feature and get cheaper white tiles as a surround.