Peripheral

Is this effect also accompanied by a loss of
proper focus anywhere on the display??
Usually an transistor that is part of the
electron-gun for a particular color begins to
fail and its capabilites are at first non-
linear and color can be lost in some area
of the display. That is if this is a
Cathode Ray Tube. The final phase of
failure is the loss of that color on the whole
display. A can of freeze spray would locate
the device and replacement would be a snap
for a skilled technician. But far better to
replace the whole unit.