An audio signal-processing system has signal-processing units connectable to a transmission line. Each signal-processing unit has channels for applying a signal process to input audio signals. A control unit is connectable to the transmission line for operating a target channel belonging to one of the signal-processing units. The control unit has color pallets different from each other and previously selected in correspondence to the signal-processing units. When the control unit detects an instruction to display an operation screen of the target channel, the control unit renders the operation screen of the target channel using the color pallet corresponding to the signal-processing unit to which the target channel belongs, so that a background color of the operation screen of the target channel displayed on a display part of the control unit is different from a background color of an operation screen of another channel belonging to another signal-processing unit.