- Humans have three cone types (S, M, L) with overlapping sensitivity spectra, limiting normal color perception.
- Fong et al. (2025) used laser pulses to selectively stimulate only M cones, producing a novel blue-green color of unprecedented saturation.
- An optical illusion with a shrinking red circle on a blue-green background can saturate L cones, allowing a similar pure M cone experience.
- It is uncertain whether such illusions can reproduce all colors achievable by laser stimulation due to screen color gamut limitations.
- The author created an interactive tool to explore and customize these illusions, and notes they may not work for colorblind individuals.