Color induction in anomalous color vision

Chromatic perception anomalies stem from altered mechanisms for discriminating wavelengths, often linked to variations in retinal photopigment function. Although diagnostic tests typically use non-contextual stimuli to isolate specific aspects of color processing, everyday color perception is inherently shaped by contextual cues. Here, we bridged this gap by measuring color perception of achromatic target stimuli being perceived as colored through color induction from the background. Participants with protanomaly (n = 11), deuteranomaly (n = 12), and typical color vision (n = 12) completed color-matching and categorical color-labeling tasks involving chromatically induced percepts within a target stimulus embedded in eight different background hues. A leave-one-out cross-validation decoding procedure showed that hue responses were highly predictive of group membership. In addition, within the protan and deutan groups, linear regression analyses revealed systematic correlations between perceived hue and clinical severity, as measured by the Color Assessment and Diagnosis Test. Specifically, greater anomaly severity was associated with stronger clockwise shifts in circular color space for stimuli whose backgrounds lay along the red-green axis. Importantly, shifts in matching responses were mirrored in categorical labeling, demonstrating that induction affects both continuous and discrete dimensions of color perception. Taken together, these findings indicate that chromatic induction can differentiate between different anomalous color vision capturing not only anomaly type but also severity along a continuous scale.