Linguistic and extralinguistic markers of schizophrenia has always been the focus of attention of researchers. Various studies have been conducted at all language levels to reveal features of schizophrenic speech. Another interesting research direction is the colour analysis of drawings by patients diagnosed with schizophrenia. This article considers colour preferences in schizophrenic speech. We employed computational methods to compile a corpus of schizophrenic texts using forum posts written by people with schizophrenia. The obtained corpus included 6.2 million tokens making it the largest corpus of schizophrenic written speech. Then, the analysis was performed to reveal what colours are preferred in the texts. The list of target colours consisted of 3 achromatic (white, black, gray) and 8 chromatic colours (red, orange, yellow, green, light blue, dark blue, violet and brown). These colours include the most archetypal ones and those studied in patients’ drawings before. The obtained results on colour preferences in schizophrenic speech corpus were compared with those obtained based on reference corpora (GICR and GBN). It was revealed that people with schizophrenia tend to use more achromatic colours than chromatic ones: 70% of colours in the schizophrenic corpus were achromatic comparable to 48.7% and 52.8% in GICR and GBN, correspondingly. We also revealed that the percentage of red, yellow, and light blue was slightly higher in the schizophrenic texts than in the reference corpora. The percentage of green and brown is noticeably reduced; the percentage of orange is slightly reduced. Violet did not occur in the forum texts even once. Finally, the percentage of dark blue does not differ from its percentage in the reference corpora.