In the channel-plate CRT, the problems of colour selection are entirely different from those in conventional CRTs because of the separation of addressing and light generation. Three methods of achieving colour selection are at present being investigated. The ‘dots-and-rings’ method uses the property that the shape of the beams emerging from the channels is annular and controlled by the output electric field. An electrode system has been developed to direct the output electrons onto one of three colours, deposited on the screen as an array of dots, each surrounded by two rings. With the second method, the electrons emerging from the channels are focused into lines which can be deflected onto an array of phosphor stripes in the three colours. Colour selection can also be achieved using penetron screens. The channel-multiplier CRT has the advantage over conventional penetron tubes that deflection sensitivity does not change with colour.