In emotion-color synesthesia, feelings have hues: a particular anxiety is olive, a particular joy is orange, and sometimes the color appears around people expressing the emotion. Researchers who study it note that it can look, from outside, like the mystical claim of seeing auras, while behaving experimentally like ordinary synesthesia: consistent, involuntary, and idiosyncratic.
The form matters to the field because the trigger is internal state rather than external stimulus, stretching the standard inducer-concurrent model. It also illustrates how synesthesia can be misread as something supernatural when it is a stable trait of perception.