TETRACHROMACY — FOUR RECEPTOR COLOUR VISION

VISUAL STYLE: A world seen through four colour receptors instead of three — the visual experience of the estimated 12% of women who may possess a fourth cone type, sensitive to wavelengths between red and green that normal trichromatic vision cannot distinguish. A dimension of colour invisible to most humans, made visible here.

COLOUR PALETTE: The challenge: representing a colour dimension that trichromatic vision cannot perceive. The solution — suggest the extra dimension through colour relationships that trichromats perceive as similar but tetrachromats perceive as radically different. Two surfaces that appear identical orange to normal vision — one warm-biased, one cool-biased at the invisible wavelength — are rendered here as clearly distinct. The fourth dimension of colour is shown as a shimmer of differentiation within what normal vision sees as uniform: a flower petal that appears solid red becomes a complex map of red-variants invisible to three-receptor vision.

THE INVISIBLE BAND: The fourth receptor responds to wavelengths approximately 545–575nm — between the standard red and green receptors. This band is visualised as a subtle additional layer of colour information overlaid on normal colour space — a shimmer of distinction within what looks uniform to trichromats.

SUBJECTS: Natural subjects where tetrachromatic advantage is documented — flower petals (which carry UV and near-infrared patterns visible to some animals), human skin (where subtle vascular patterns become visible), feathers and iridescent surfaces (where structural colour reveals additional layers of pattern).

REVELATION: The central visual event is the moment of seeing more — a surface that appears uniform suddenly differentiated, colour distinction where there was colour uniformity. The fourth receptor switches on and the world becomes more complex.

No photographs. No real people shown. Pure colour science, pure expanded perception, pure fourth dimension of colour experience throughout.