If those are the only choices then black for sure

I would do dark brown...definitely not white.

task lighting plugmold offer a bronze. That's what I would do.

Black.

I haven't seen it in a brown or bronze. And I have searched high and low, finding few online sources. Can anyone help me with a link?

BTW, this is across an aisle from the sink, so it doesn't face the open, and thus it won't be very visible to the visiting public.

I would like to just do an outlet, but the construction of the side of the cabinets (drawers and glides) doesn't allow sufficient space for even a slim electrical box.

Task Lighting and their angled plugmold strips are available on Amazon or Hardware Resources. Search for APT in whatever size and color you want.

click below

https://www.amazon.com/Task-Angled-Power-Strip-Bronze/dp/B084L1LC2W?th=1

Do NOT by this product from Amazon. Visit your local electrical distributor & ask for plug mold from Legrand.

Black, since it doesn't go under all of the counter.

Beautiful furniture in the background!

20 years ago when we remodeled our kitchen we put outlet strips under the cabinets because we didn't want them in the back splash. Way back then, only white was available so I took them to a body shop and had them painted. There are so many more options now I'm sure you can find what you need but in case you can't that might be an option for you.

We got a good match from Lutron, color Sienna might work for you. I ordered free color samples from their website. They have a couple of different shades of brown to choose from. Our cabinet maker said he uses it all the time. https://www.lutron.com/en-US/Residential-Commercial-Solutions/Pages/Residential-Solutions/ColorStyleFabrics/Color.aspx

If they don't have what you need then I would definitely go dark. Dark colors recede and light colors advance, so you'd want it to recede into the background and not stop your eye right there.