If they are showing a colour they cannot be 'dead'
If one thinks about what goes on, when a screen illuminates[be it CRT or TFT]
White is 'All Colours ON'
Black is 'All colours OFF'
All tones and shades are the rapid switching between 5 modes
RGB On/Off as appropriate
Therefore a few colours remaining on in the 'Off'
mode may not be the screen at all but some kind of data transfer or interference from the computer.
The way to find out is to try the screen on another computer.
You may get another kind of result.