Colour agnosia

Color agnosia (from the Greek ἀγνωσία agnōsia, "ignorance" or "non-knowledge"), is a medical or psychological condition that prevents a person from correctly associating hue names with common objects. The sufferer retains the ability of distinguishing hues. It is a specific form of agnosia and generally results from damage to the visual cortex, often in V4 (as opposed to most other kinds of color blindness, which stem from problems with the photoreceptor cells).