They create a rustic contrast with the smooth, light-color plaster walls.
For example I think the scaffold will probably be a light color because source 4 seems pretty reliable.
Since it is ivory, the light color is likely to show any stains or blemishes in the surface of the desk.
Pick up a light color from the counters in dark kitchens, or choose a dark shade for kitchens that get lots of light and which have a counter with a bold hue to offset it.
Paint the walls a light color or a neutral shade.