If you are indeed getting inverted colors (see below), it is probably that you have a "negative logic" monitor (most likely if the game was a Nintendo game, or a monitor for a nintendo game converted to something else). If this is the case, you will need a video inverter for each color (red, green, and blue). Go to
http://www.arcadecollecting.com/info/Nintendo-color-invert.txt for the details of an inverter.
If you are indeed missing a color (see below), you probably have a problem with your video circutry inside the monitor, or bad wiring.
Inverted Colors: If your video is inverted, your monitor will output the following way:
Red -> Cyan
Green -> Magenta
Blue -> Yellow
Cyan -> Red
Magenta -> Green
Yellow -> Blue
White -> Black
Missing a Color or Colors: If your monitor is missing colors, use the response table below to determine which color is missing.
Missing Red:
Red -> Black
Green -> Green
Blue -> Blue
Cyan -> Cyan
Magenta -> Blue
Yellow -> Green
White -> Cyan
Missing Green:
Red -> Red
Green -> Black
Blue -> Blue
Cyan -> Blue
Magenta ->Magenta
Yellow -> Red
White -> Magenta
Missing Blue:
Red -> Red
Green -> Green
Blue -> Black
Cyan -> Green
Magenta -> Red
Yellow -> Yellow
White -> Yellow
Missing Red and Green:
Red -> Black
Green -> Black
Blue -> Blue
Cyan -> Blue
Magenta -> Blue
Yellow -> Black
White -> Blue
Missing Red and Blue:
Red -> Black
Green -> Green
Blue -> Black
Cyan -> Green
Magenta -> Black
Yellow -> Green
White -> Green
Missing Green and Blue:
Red -> Red
Green -> Black
Blue -> Black
Cyan -> Black
Magenta -> Red
Yellow -> Red
White -> Red
Hope this helps