Color issues
Incorrect colors can have various causes. In order of probability: bad JAMMA contacts or wiring, broken SCART cable, monitor failure, damaged video DAC, bad palette RAM, cut traces between GPU chips (check P bus)...
The color test screen in the system ROM menu can help diagnose problems (burnt DAC resistors...).
Example screenshots are from Blue's Journey.
One missing component
-
Turquoise "cold" image means no red
-
Purple image means no green
-
Orange "hot" image means no blue
Two missing components
-
Green and blue missing
-
Red and blue missing
-
Red and green missing
Three missing components
Enjoy the sound :)
Sync missing
Rolling or distorted display, most probably a bad contact. If not, check SYNC.