This post explores the fascinating concept of perceiving "new" colors beyond the normal human visual spectrum. It begins by explaining the overlapping sensitivity of human cone cells, which prevents the experience of single-cone activation. The author then introduces a scientific study by Fong et al. (2025) that used laser pulses to selectively stimulate individual M-cones, resulting in subjects reporting a "blue-green of unprecedented saturation."
The post then shifts to discuss optical illusions, specifically the "Eclipse of Titan" illusion, which can induce a similar intense blue-green hallucination by desensitizing red-sensitive L-cones, allowing green-sensitive M-cones to fire in isolation. A key question is posed: Can these optical illusions truly replicate the "new" colors achievable with direct laser stimulation? The author delves into color gamuts (LMS and sRGB) to explain the limitations of both human perception and electronic displays in producing or representing these theoretical "pure" colors. While direct laser stimulation definitively expands the perceived color space, the author suggests illusions on screens might only push the boundaries slightly, if at all, due to technological constraints. Finally, an interactive tool is provided for readers to experiment with various color-inducing optical illusions.
Exploring the Spectrum: Unlocking New Colors Through Lasers and Illusions
Human Color Perception Limitations: The human eye uses three types of cone cells (S, M, L) whose sensitivity spectra largely overlap, preventing the natural experience of perceiving colors from the activation of a single cone type in isolation.
Laser-Induced Novel Colors: Research by Fong et al. (2025) demonstrated that selectively stimulating M-cones with laser pulses allowed subjects to perceive a "blue-green of unprecedented saturation," a color that cannot naturally occur.
Optical Illusions Mimic Pure Cone Activation: Optical illusions, like Skytopia's Eclipse of Titan, can induce similar "new" color perceptions. By staring at a shrinking red circle on a bluish-green background, the red-sensitive L-cones are desensitized, allowing the green-sensitive M-cones to fire more exclusively, creating an intense, hallucinated blue-green.
Gamut Boundaries and Display Limitations: The natural human color gamut is limited by the overlapping cone sensitivities. Standard sRGB displays used in electronic devices represent an even smaller subset of these colors, as they cannot produce single wavelengths of light.
Uncertainty of Illusion's Effect: It remains unclear if optical illusions viewed on screens can truly take perception outside the natural human color gamut, or only slightly expand it, due to the inherent limitations of display technology and the complexities of cone saturation.
Interactive Exploration Tool: The author has created a web-based tool allowing users to customize and experiment with various color-inducing optical illusions, including adjusting colors, sizes, and animation speeds.
Implications for Colorblindness: The author notes potential (though unconfirmed) applications of these illusions for individuals with colorblindness, such as deuteranomaly, by selectively activating their cones.