Archibald Thorburn is high-key - luminous, open, and weighted toward light. Cool tones set the register here - the blues and greens easily outweigh any warm accents. Chroma is kept low across all colours, producing the soft, enveloping quality that characterises tonal painting. #77471C functions as the palette's exclamation mark: highest chroma, lowest percentage (3.2%). 60 units of value range underpin the palette's structural clarity: the eye always knows where light falls. The mid-to-high key, cool bias, and moderate chroma point to outdoor observation - sky and diffused daylight as the dominant light source. Palette 3 sits within the larger chromatic argument that Archibald Thorburn's complete body of work advances.