Abstract: A tri-color video signal generator, for use with either a color or black and white standard television receiver, includes a circuit for producing the color signals R, V, B and a matrix circuit for producing a luminance signal Y from the color signals. The generator further includes circuitry for modifying the respective proportions of the R, V, B color signals in the luminance signal Y whereby in a black and white receiving mode, the grey scale of the luminance signal Y is modified making it possible to accentuate the contrast between the picture elements whose original colors would have been converted into luminance levels which are very near one another.