• Blue

• Wavelength: 450-495 nm
• Emotion: interest
• the color of distance, depth, and exploration
• evolutionary signal: sky, ocean, open water — safe horizons worth investigating

• properties

  • lowers heart rate, reduces anxiety — the physiological opposite of red
  • promotes focused attention and creative thinking
  • the color of Rayleigh scattering — the sky is blue because short wavelengths scatter more

• in nature

  • sky: the infinite frontier, the invitation to explore
  • ocean: depth, mystery, resources, travel routes
  • clear water: safe to drink, rich in fish
  • rare in land organisms — blue pigment is uncommon, often structural color (morpho butterflies)

• in prism

  • exploration, curiosity, unvisited territory, new particles to discover
  • the color of search — the drive that powers the main loop