Bocci outlets, although there has been some discussion as to whether they are to code in all applications.

You can get colored outlets...these are the ones I used for my bathrooms Leviton RGF15-RN 15 Amp Renu Self-Test Tamper-Resistant GFCI Outlet in Rich Navy https://www.amazon.com/dp/B01LYKFC0Q/ref=cm_sw_r_cp_api_i_BnwZDbXRWYY5B

Black, brown or dark grey outlets?

Are there any other colours in your kitchen? What are the counter tops?

I thought "navy" meant the island was the size of an aircraft carrier (like what I have seen here on Houzz).

Leviton has a wide variety of colors including Rich Navy:

https://store.leviton.com/products/renu-15a-self-test-tamper-resistant-gfci-outlet-rgf15?variant=28151128771

https://store.leviton.com/products/renu-one-gang-screwless-snap-on-wallplate-rewp1?_pos=16&_sid=e97d56964&_ss=r&variant=18216750403

Bocci are expensive. The Leviton may work. Any other ideas?

The counters and backsplash are white.

White:

Navy is a Neutral Ranch Remodel & Addition · More Info

Gray:

Open Concept Kitchen and Living Room · More Info

Black:

If you have stainless steel appliances, maybe having stainless steel covers with a grey outlet.

If these outlets are just there to satisfy code and won't be often used, you could use a stainless steel pop out outlet for a cleaner look (but less convenient to use).

We used navy outlets. Pretty close match and I like it better than any of the others shown.

I've painted outlets to match before without any issues (despite years of use). YMMV.

Plug mold up under the edge of the counter overhang

https://www.google.com/search?q=wood+paintable+outlet+covers&client=firefox-b-1-d&source=lnms&sa=X&ved=0ahUKEwjBjsGrkurlAhWi1FkKHX8NBtwQ_AUIDCgA&biw=1536&bih=713&dpr=1.25

Plug molds are the way to go. Not only are they near invisible, when you don't want to see them, they also have the advantage that they allow you to install lots of outlets, so you never have to hunt for an unused one.

All our kitchen outlets are plugmolds. I love it. Leaves our backsplash completely free of any obstruction. The downside is that any permanently plugged-in appliance has their powercord more visible. But we try to keep our counters empty as much as possible. So, there are very few countertop appliances. We do have a small appliance garage for some of them, though.

Are you going for the industrial look?

LOL. I hadn't thought of that possibility. Yeah, I guess if you don't have uppers nor have an island with some sort of overhang, then that's what you are stuck with.

It is kinda cute in industrial way. But no, I don't think most people would like this.

My island is blue, but not navy. We went with black outlet and stainless cover. Depending where the placement is, you won’t notice them IMO. When placed on an end that is highly visible is what is objectionable to me. Mine are on the working sides of the island.

If the Lutron navy isn't the right color, you could get paintable wall plates and paint them to match the island. With black outlets or maybe the Lutron rich navy outlets, they should blend well with the island.

Now that plug mold was mentioned I will forever loath the outlets on my backsplash and island.

Hoping builders and electricians are paying attention

Sillites are much like the Boccis posted, but come with snap-on covers you paint to precisely match your cabinetry or tile. Nearly Invisible. I had no problems passing code.

You can buy paintable covers. I have a ridiculous amount of outlets on my backsplash so we did this and it looks so much better. Prime and paint. Also painted the screws with an artist brush

https://www.amazon.com/Taymac-2000W-Paintable-Outlet-1-Gang/dp/tech-data/B000SL2C9I

Bought ours at Home Depot.

Arnev will make switchplates to your specifications (edges, orientation, wood grain, etc) that you can have stained or painted to match your island (wood).

Arnev.com

Black

If you are a University of Michigan fan you could go with maize . . . as tacky as that would look.