We have a similar paint color in our master bath (medium oak cabinet instead of dark) and for years I had dark blue and rose towels. They've finally worn out and I was really sick of the rose, so I went looking for a "splash of color". I went to Target and bought a floor rug in every single color, except burgundy because it doesn't go with the new color scheme in the bedroom which is greens and blues, they had in the Waverly line (their Thomas O'Brien and Fieldcrest lines are great, but costs twice as much and we're not really that hard on towels). DH and I laid them out and analyzed. A few we ruled out right away. DH didn't like the Hotel Gold, but that might work for you with the yellowish sink top. We settled on Loch Ness, a mossy green shade. I wouldn't have thought it would work, but it did. You might try the burgundy as well. Anyhow, the cashier looked at me kind of funny when I checked out 8 different colors of the same rug, but she understood when I explained. It really helped to see them firsthand. I was surprised by what we ended up choosing, but like it very much.

Well, lighting is everything when it comes to paint, so if the lighting in the basement is causing the other two to blend, then the color you want for the accent wall needs a lower LRV and more depth. So, LRV for Moonshine is 67.36; Palladian Blue is 61.14; Yarmouth Blue is 55.57, so the Yarmouth Blue is going to contrast with the Moonshine much more than the Palladian Blue, but it's still above the 50% line so that it will give off light more than it absorbs. Might be a good choice. It's bluer, though, than the Palladian blue.

My daughter has Coventry and I love it but agree it has blue in it. I also like Revere Pewter but it does read beige grey. Other grey's that don't read beige and don't have blue in them are BM Sea Haze 2137-50 and gray owl on same strip 2137-60. I see some green undertones in them. Ozark shadows AC 26 has less beige than Revere Pewter with no blue. It's also about as deep as Coventry. Harbor gray, one lighter on strip AC 25 looks more true grey but lighter than Coventry. I know you said no purple undertone, but my neighbor used a beautiful grey called Valspar Smooth Pebble, which looks like a beautiful med. grey in her bedroom. I wouldn't have realized it had purple undertones until we tried to have it mixed by BM. They screwed it up and it showed alot of purple on the swatch we painted on the wall. However, even as badly mixed as it was, once it dried , it dried a nice grey. But we didn't give it a chance cause we freaked cause her bedroom was painted purple prior to the grey. So she went with coventry. also, Silver Fox BM2108-50 is a popular grey but I do see purple/tan undertones, much like the Valspar color. I would try Silver Fox, Valspar smooth pebble and Ozark Shadows. If you want lighter and tanner, then Revere Pewter.

Regarding color matching. Part of the reason so many people have such different experiences is because it depends on the paint store person. If you DO NOT hand them a chip and say "match this" some of them will look up the closest match and give it to you because they figure if you don't have a chip, you have no clue if it's a match or not. And it's easier for them. When SW Nomadic Desert was a popular color, this happened often. BenM stores wouldn't even try to match the colors, they'd just make Sierra Hills and say it was Nomadic. If you asked for Latte you'd get Hillsborough Beige. People were none the wiser and then couldn't figure out why their "Latte" looked so different from what they saw at a friends house or seemed so different from the vibe the color even had in online pictures. If you have a chip, then they can't substitute their closest match. They have a target to match. You can order chips for free online. https://www.sherwin-williams.com/architects-specifiers-designers/color-samples https://www.benjaminmoore.com/en-us/order-color-sheets And all the spin you hear about paint chips not being "real paint" and not as good as hand-painted samples is ridiculous. The paint chips have to meet rigorous quality control for color accuracy; the production standards are seriously hard-core color management. What do you think they use for a target, a point of control, to mix the paint used to paint those hand-painted samples? Think about that for a minute.....