Pink Day

What the day is

Pink Day is observed on June 23. Pink is a stranger color than it looks, starting with the fact that it does not appear in a rainbow.

Origin and background

Run sunlight through a prism and the spectrum runs from red to violet with every wavelength in between. Pink is not among them, and no wavelength of light produces it. Pink is what the visual system reports when the red-sensitive and blue-sensitive cones are stimulated while the green-sensitive ones are comparatively quiet, a combination that light from opposite ends of the spectrum can produce but no single wavelength can. It belongs to a small group of colors that exist only as mixtures, which is how the visual system closes the hue circle into a loop rather than leaving it a line.

Saying pink is not real goes too far. It is exactly as real as any other color, since all color is a construction of the nervous system rather than a property of light. Pink is simply unusually honest about it.

Its social history is equally unstable. Early twentieth century American retail advice recommended pink for boys, on the reasoning that it was a stronger and more decided color, being a lesser form of red, with blue suggested for girls as the daintier option. The modern coding settled in around the middle of the century and hardened commercially after that. A convention that feels ancient is roughly seventy years old and once ran the other way.

One much-repeated claim deserves care. A particular shade of pink was painted in holding cells in the late 1970s on the basis that it reduced aggression, and it spread widely on the strength of early reports. Attempts to replicate the effect have largely failed, and the current view is that the evidence does not support it.

How to take part

• Look for pink in a rainbow, and note that it is not there.
• Read about the pre-war advice that assigned pink to boys.
• Treat the calming-pink claim as unproven.
• Notice how much pink in a store is a marketing decision, not a preference.