A multicolor inked ribbon cartridge for an impact serial printer comprising a ribbon housing body and two arms protruding from such body to allow the interposition of a ribbon portion between a printing head and a printing support for the whole length of the platen when the cartridge is rotatably attached to the frame of an impact serial printer by means of two lateral cylindrically-shaped projections provided on the body of a cartridge thus permitting rotation of the body around a common axis of said cylindrical projections, parallel to the platen. The cartridge rotation around such axis and therefore the positioning of a suitable multicolor band between the printing head and printing support is assured by a cam actuated by a motor and interacting with the body of such cartridge. The cartridge is further provided with a string made tight between the ends of its arms upon the multicolor ribbon portion which is interposed between the head and printing support. Such string is provided for slidably and rotatably attaching a ribbon positioning and guiding element, which follows the cartridge rotation, and at the same time, is suitably coupled to the carriage of the serial printer, to follow the printing head in its transverse shift in order to assure a correct positioning and tensioning of the subsequent zones of the multicolor ribbon contacted by the printing head.