synesthesia

Synesthesia: hearing colour, seeing sound

Synesthesia is a neurological phenomenon where one sensory experience is automatically accompanied by another. The most common is colour synesthesia and chromesthesia. Colour synesthesia is where for example letters, numbers or weekdays gets a colour automatically "attached". Tuesdays might be purple, the number 9 red or things like that. It is automatic, involuntarily. People with colour synesthesia can remember phone numbers ...