Art Nouveau is strongly light-biased - shadow is suggested rather than declared. Built on cool foundations: the palette favours the blue-cyan-green arc. Chroma is moderate: colours carry enough saturation to be read as colour, but the palette stops well short of garish intensity. At 4.0%, #C56740 carries the palette's sharpest chromatic charge: an accent that earns its place precisely because it is withheld. Value range is moderate at 47 units - enough contrast for legibility, not so much as to fragment the tonal unity. High luminosity and cool temperature suggest the plein-air condition: unfiltered daylight and open sky.