If you're trying to keep the same look then I think #3 looks best with your choice.

One suggestion? Make sure you have some "drop" room on both sides of the prep sink. I know for myself, I'll put the unwashed stuff on one side, wash it and then transfer to the opposite side of the sink.

First, I'd move the prep sink in toward the center of the island by at least 12", preferably 18". This will give you landing space on both sides of the sink and minimize, if not totally prevent, splashing water onto the floor - especially important if you have a wood floor, but important regardless of the floor material.

Prep sink...IF they have the same interior dimensions (width & depth front-to-back & depth top of sink to bottom of sink), then I would go with #2 b/c you will have a bit more room in the sink. [If the sink was against the wall, I would have said #1 to give you more space for the faucet.]

Colander...since the sinks are two different sizes, I doubt you will find one to fit both - unless you can find one that expands/contracts.

Honestly? I'd rather have the larger sink than be matchy-matchy on the sinks. They're far enough away that it won't matter. (Plus, the rounded corners will be much easier to clean than those in your cleanup sink or your #3 choice.)

No prep sink should be less than 17" or so wide (preferably > 18") - that's if you plan to prep at it, not just use it as a bar sink. I strongly recommend you go with the largest you can fit. Your island is plenty wide enough for the wider sink.

I have a "D" shaped cleanup sink and a rectangular prep sink - no one has ever said, "gee, why don't they match?". If it's undermount - then no one will notice anyway!

Oh, and move the trash pullout to the island. It can be on the end closest to the cleanup sink for sharing. You generate far more trash and recyclables when prepping and cooking than you do while cleaning up - and for a much, much longer period of time.

By far, my biggest regret in my Kitchen is that I put my trash pullout next to my cleanup sink and not in the Prep Zone near my prep sink!

Is 15" sufficient for a prep sink? '

Or I have to go with a clean up sink like the Kraus KBU14E, 31.5" and 18.38" vs 32" and 19" plus an off set drain. I do like the squarer one for a streamlined look tho.

I know I mentioned to leave space to the left of the sink but I see it doesn't reflect on these plans. I have to remind myself to follow up on that on monday.

@buehl: the trash is in the far end of the island, left to the clean up sink is the dishwasher.

Plenty of room with a 15" square sink. The diagonal is twenty-one inches. Make a list of what can't be prepped there. Breaking down that carcass will need the main sink anyway.

My prep sink is 17-3/4" x 17-3/4" (interior) and it's too small. It's usable, but not the best. When we build again, I plan to find one at least 21" interior width.

Just about the colander comment - I would not base my sink decision on an accessory like that. For one thing, as Buehl said, you can find expandable over-the-sink colanders like this one (there are many others). But I have one of those, and it ends up that my actual go-to colander is a regular round one with feet that sits in the sink while draining and is put away otherwise.

buehl why do you find it too small? I'm asking because the one I'm getting is the size you have.

Some large kitchens with multiple cooks or some kind of personal anomaly of the owner could include two main sinks and no prep sink. This size kitchen with the island counter dimension it probably has can work great and retain good function and proportional design with a 15x15 sink. This island may have seating and other functions. Again make a list of what can't easily be regularly prepped with that Kohler sink. Nothing yet.

CPArtist...there's really not enough room for food and hands in the sink and still have room to manipulate the food and prep tool(s). Some things are ok...like just cleaning fruit and vegetables, but if you need to do anything else, there isn't enough room. It's also too small for some of my colanders.

What is the function/purpose of a D-shaped sink?

the D shaped sink was the first "singlebowl" that really caught on. The drain/disposal is set back,allowing more usable space in the cabinet. The curve and ample counter areas around the back corners allow offsetting the faucet so the dimension front to back can be generous, getting a lot of sink for not necessarily a huge side to side measurement. There are many other single bowl configurations now....A deep single D sink is still a good option...among all the others.

And here's others 11" 5qt 9.5" 4qt 8.5" 3qt