The inability to tell similar colours apart, which cannot be explained by reduced contrast sensitivity, or difficulties learning the concept of colours or colour names due to other CVIs alone has been shown experimentally to be due to impaired colour vision. There are at present no clinical tests to identify this issue, but it is likely to be impaired in children with more severe cerebral visual impairment. Further reading What Is CVI? The Image, Colour, Lesson 5d Colours, COOL Games (colour concept and naming game).