Susan Jablon Mosaics custom blender lets you play with grout color- you might want to check there and see if anything appeals to you.

Either a beige, like Mapei's bone or something similar, or a soft gray, like Mapei's Warm Gray. Either one would allow the tile to really pop.

Maybe something in one of the yellow shades, to blend in with the tile? It all depends on how noticeable you want the grout to be. You can choose something to make the tile pop, as Bill suggested, or go for something that will blend in and fade away color-wise. No right or wrong, just your preference.

Thanks for the feedback!
Just picked up 2 different "TEC" grout colors: "sand" and taupe grey... I was really looking to NOT having the grout lines stand out but let the breaking light (from under cabinet halogen lights) really show the glass lines and shadows. Well, I'll do a 'dry test' today and will post the finished product later.