Probably nothing more than your color settings being a little off,
which is usually easily adjustable on LCD monitors.
On older CRT monitors, it may indicate that the color tubes are fading or burning out.

Top left colors : grey, white and red		Top right colors : green and black.
Bottom left colors : black and yellow		Bottom right colors : navy blue, white and lavender (light purple)

For reference, the left side background of this page is a medium dark teal green, (like ocean water)
whereas the middle and right side of the background color is a medium grey color which is different than the top left grey.
I chose these colors to represent the differences in monitors I've seen all over.
Can you see the shadowing of "Eric-Tech" in the topleft corner?