Abstract: A Thermally transferable ink sheet comprises a base film having a periodically repeating set of successive ink coated regions having a plurality of color inks thereon, and index mark regions whose index mark comprises a combination of a plurality of sensor marks indicating information regarding the ink sheet located at each border between adjacent ink coated regions. According to a preferred embodiment, each pair of adjacent ink coated regions juxtaposed across each border have extended portions extending toward each other into the index mark region in directions parallel to the direction of ink sheet feeding. Thus, it is possible to read the index mark and identify the ink colors of adjacent ink coated regions at the same time. According to another feature, two sets of index marks are provided contiguous to each other to allow the print apparatus to be controlled by the combination of the resultant readings obtained separately from both sets of index marks.