Colored hearing is what the 19th century called chromesthesia. French researchers wrote of audition coloree, German ones of Farbenhoren, and the case reports they collected still read accurately today: specific voices, keys, and instruments arriving with specific colors, consistent per person.
The old term survives in citations and translations, so anyone reading the historical literature meets it quickly. The visual experiences it describes are photisms, and the modern experimental work on the phenomenon is covered in our chromesthesia explainer.