Colour blindness was correlated to the severity of schizophrenic symptoms only in the subgroup of patients with severe schizophrenia.Conclusion: Colour vision defect is a common feature in schizophrenia, and may be more significant when related to psychotic symptoms.KEY POINTSA significantly higher mean TES was found in schizophrenics compared to healthy patients.Colour blindness was correlated to the severity of schizophrenic symptoms only in the subgroup of patients with severe schizophrenia.Colour vision defect is a common feature in schizophrenia, and may be more significant when related to psychotic symptoms....