Archibald Thorburn is high in key: pale, luminous, and filled with optical air. Blues and teal-greys govern the palette, lending it an aquatic or atmospheric quality. All colours lean toward grey, building depth through value rather than colour punch. Archibald Thorburn gives 31.1% of the composition to a single #BFC3C1 - a decisive chromatic anchor. At 10.0%, #C9BC9C carries the palette's sharpest chromatic charge: an accent that earns its place precisely because it is withheld. From deepest dark to palest light, the palette traverses 64 units of the value scale - a span that creates natural depth. High luminosity and cool temperature suggest the plein-air condition: unfiltered daylight and open sky. In the context of Archibald Thorburn's full range of palettes, group 4 represents one movement in an ongoing chromatic dialogue.