A data storage medium comprising recording information in the form of a track of data points, the colour of each data point being selected from at least three different colours, wherein the recording information is disposed on a substrate which comprises a colour forming composition, wherein said colour forming comprises a colour former which is susceptible to changing to at least three different colours when irradiated with a laser, wherein the colour former is a leuco dye, a diacetylene or a carbazole. Methods of forming the data storage medium and methods of reading the medium are also provided.