a white tile. a subway, an arabesque, a penny round.

I probably would also go with white and not play up the green/gray that you are not crazy about.

As mentioned above, try white, but also consider a grey. I would bring home a ton of samples to really get a feel of the look you would like and what works best with the color tons in the counter.

Pebble Grey 3x6 Glass Subway Tiles, 10 Sq. Ft. · More Info