Abstract: Generation of a switching signal for the chroma keying of color video signals, in which generation the voltage level of the switching signal becomes a maximum for a selected hue. The switching signal corresponds, when an adjustable voltage level is exceeded, to a specific color saturation of the selected hue. This generation is carried out by means of a first and a second color difference signal derived from primary signals of a color signal source, and by means of a sine-shaped and cosine-shaped variable control signal, the variation of which is a function of the angle of the selected hue in a color spectrum. In this generation, the first color difference signal is multiplied by the sine-shaped control signal, and the second color difference signal is multiplied by the cosine-shaped control signal, and the multiplied signals are added to a first signal component.