I've found my color.
You can see it in the dark windows against the white wall below, in the wires and cables stretching to the backs of the houses, in the shadows and the ironwork balcony on the right. "Slate" is no. 376, second from the right on the wall.
I had a strong preference for the gray (518) earlier in this process. That color is much less blue than it appears in the photo, tending toward taupe. But I think the Slate resonates with the environment, and I do think it will work well with the plants, especially after some green vines attach themselves to the wall.
Below you can also see how the darker color takes on a grayness when sunlight strikes it at a certain angle. That grayish reflective surface, changing with the light, will make for a satisfying background to the plants, and add richness and depth.
I bought the Slate stain this afternoon and expect the contractor to have the walls painted soon, though the forecast for rain tomorrow may delay that. I'm hoping the warm weather continues for a while so this can be finished.
For what it's worth, below are the three new colors I tried earlier this week: Forest from Behr, Jasper and Charleston Green from Sherwin Williams. Forest looks very olive, much more so than you can see in the photo. Both Jasper and Charleston Green appear to have a lot of blue in the photo, but they don't.
Without first trying these colors, I don't think I'd have been ready to choose Slate. But when I looked at the array of colors this morning, and at the surroundings (not lovely but with their own color palette), the decision was immediate.
On another subject, but related because it does illustrate how important shadow will be in this little garden, I'm thinking of using this old, cracked, round fountain as a planter. I originally thought it would be inappropriate, but it may work if planted with mosses, small ferns, and other things. Most of it will disappear. I may need to pump a trickle of water to keep it moist. Just an idea. We'll see ...
By the way, that motion-activated security light over the center of the doorway is coming down. It's supposed to be off to the side, as invisible as possible.
And looking away from the house, the back of the garden badly needs a point of focus, a feature to draw the eye. Something on axis and with height. I have an idea I'm working on. Saint-Gaudens used a similar concept for a focal point in his garden in Cornish, New Hampshire (not that I'm claiming his robe, but one can imitate a good idea when it comes freely, no?).