gold, that's very similar to mine. I did the Eternal Serena, and a Calacatta on the islandAnd I have no friggin idea which one to pick for mine!
don't be so worried about the island slab. the tile will border the gray one. the cooler one is further away, so it will all blend. Your cement tile idea is a good one. just find a gray (or black/white and gray) that works w/your perimeter, and it will be fine. I mean, I'm considering these for just the bar area. the island marble is the same that's on the bar. (I just have these leaning against the wall. there will be one more shelf on the left, and of course I'd do the entire wall)
you could do any of these and they would work
Q