The aim of the present study was to determine, through colorimetric analysis, whether schooltextbooks for children aged 5 to 7 years contained tasks requiring normal colour vision discrimination fortheir resolution. In addition, the performance of a group of observers with diverse colour vision deficiencieswas evaluated while conducting the tasks under analysis.Results: Textbooks of mathematics were found to include 10% of tasks which, to an observer with colour visiondeficiency, would be very difficult or impossible to solve. The level of difficulty of each task was influenced bythe type and degree of colour vision deficiency and by the actual ambient illumination under which it wasobserved.Conclusions: Some school textbooks need to be redesigned through an alternative use of colours and texturesto take into consideration colour vision deficiencies. In view of the present findings, many Spanish editorialboards have committed to undertake these changes.