colour killer BrE
color killer AmE

The "damaged" signal triggered the "colour killer" mechanism, installed in colour TV sets to prevent the appearance of incidental colour spots on the screen when black-and-white films are broadcast or when the reception is disturbed.

The "damaged" signal triggered the "color killer" mechanism, installed in color TV sets to prevent the appearance of color.

And without a protective coating of sebum, hair becomes drier (so it looks duller) and more susceptible to color killers like sun and salt.

The color killer is an electronic stage in color TV receiver sets which acts as a muting circuit to cut off the color amplifiers when the TV receives a monochrome signal.

The color killer is actually a muting circuit in the chroma section which supervises the burst and turns off the color amplifiers if no burst is received (i.e. when the signal is received signal is monochromatic.)