If you're looking to inject some color, one possibility would be an apple green color. Something like a quartz countertop in an apple martini, with a green glass mosaic backsplash. Examples below:

http://www.sci-surfaces.com/quartz-colors

http://www.stone-services.com/blog/53-an-apple-a-day-a-green-quartz-countertop-and-a-glass-tile-mosaic.html

Marble, or marble HD laminate on countertops would look nice? We used it in our bathroom remodel, and plan to use it in our kitchen too. We went with the HD laminate as where we live not cost effective to use the real stuff. Like your cabinets, ours are stained, but had thought about painting them.

Keep the color light like what you have. Something that looks like white marble with grey veins. White subway tile backsplash or colorful tile. Check to see that the counter and tile patterns don't clash. Apple green or red would be bold and beautiful and classic white would bounce light. If you choose those multi colored tiles keep the counters in a very subtle texture.

Maybe a white or grey countertop. This is our GEOS Recycled Glass Countertop in Saint Lawrence and White Birch!

Love your grey cabinets! If you go for a darker color on the countertops, classic white subway tile would keep the light bouncing around. I like the idea of keeping light countertops on the left wall and getting darker ones in the same material on the island. Grey-green glass tiles on the backsplash could inject some color without upstaging the cabinets.

I love the idea of marble with your grey cabinets. You could do a marble look quartz if you don't want the maintenance of real marble. An alternative would be a white quartz counter with a marble backsplash. When replacing you counters I would replace your sink with an undermount.

I was also going to post that Vesta residence kellyography posted - love the soapstone.

You could also consider marble tiles, like this:

They also make a stainless subway tile that is KILLER and would look amazing in that space. Reflective is good.

To add some further interest, consider adding finishes to the front of counter bar. Picture gives you the idea. Don't be afraid to add some drama depending on your look!
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While you're at it, I would consider lowering the raised bar to counter height, it'll give the sink more space, feel more open and with some lower stools can still be used as a eating counter.

Marble, or if you are worried about maintenance Pental Quartz have just launched a range of quartz that looks like marble, beautiful!

I think you definitely need texture in the room. The glass tiles are an excellent choice per Keitha. If you don't want to spend a ton of money, there are some gorgeous laminates for the island. I think a wall color would be a good way to add interest and pull the backsplash and island countertop together. You have a lot of options for make this an outstanding room.

I would use a stainless wall tile backsplash as it would be light reflective and bring a sense of continuity to the kitchen. Then, definitely lower the island counter as it gives you so much more space and makes the kitchen seem huge. A white or black granite or marble would be nice on the counters. Use the walls as your pop of color as it is so much easier to change your color sceme with paint. You can bring the wall color into the rest of the room with window treatments, light fixtures and dishes, etc. You might even consider painting the main walls a very light gray and then paint the bay area and the soffit in the red of the picture in the living room. The red would look really nice in the shade of the light fixture and in a print for window treatments.

Glad to see this thread... I'm thinking of painting our birch cabinets gray. We already have granite with tans, gray and cream running through it. So, I believe the gray would work with the granite... My concern is, the rest of our home is very Tuscany (reds, yellows, browns and a bit of green - warm colors). The walls are a mellow cream (with a tad bit of yellow) and the light/ceiling fans are oil rubbed bronze. I'm wondering if the gray will blend or stand out awkwardly?

I think this would look fantastic as your backsplash! http://www.glasstilestore.com/shop-by-colors-now/gray/monarch-white-thassos-with-bianco-carrera-strips-marble-tile.html