I've definitely seen kitchens with islands in both a different color and different granite pattern than the rest of the cabinets and counters, but I think if your kitchen is on the small side or if you don't make quite the right choices, it has the potential to look incoherent and just too busy. Personally, I prefer a more cohesive, less busy look. So if it were my kitchen, I'd probably keep the counters consistent throughout if I were using your two cabinet colors.

My first thought would be that it will be too distracting. The last thing you want your reno to look like is that you ran out of your first material choice i.e granite/cabinet colour. Can you send photos of the kitchen. If your kitchen is big enough & you are considering an island then that could be a different base colour to your wall cabinets but it should compliment whatever you've chosen. Two different counter tops would only work if the surfaces again complimented each other, stainless steel & marble. In my opinion large fixtures in any room should be simple because these are usually expensive items you will be living with for some time. Keep us posted.

Here is a picture of the floor plan....as there is no kitchen yet!