Shortest answer:
- Everyday “blinding” brightness: pure white (all wavelengths blasted out at once).
- Single-hue champion (equal power comparison): an electric yellow-green right around 555 nm – the exact wavelength where your daytime cones hit maximum sensitivity.
Why:
- Human-eye physics
Your L- and M-cones overlap in the 540-570 nm band. The double-hit of stimulation there makes that yellow-green look super-luminous for the same physical wattage. That’s why emergency-exit signs, high-vis vests and laser pointers all skew chartreuse.
- White ≠ spectral color, but it wins on sheer photons
“White” just means all visible wavelengths reflected or emitted together. Pump enough total light out and white will drown every other hue, which is why phone screens, floodlights and the sun at noon all look white-hot.
Quick takeaway for design & visibility
- Need maximum pop with limited power? Use neon yellow-green (~#CCFF00).
- Need the absolute brightest possible output and have power to spare? Crank up broad-spectrum white.