Because blue signal is missing? I don't know
I'd agree. It looks like blue is weak/missing.
When you hooked it to a TV, did you use the RF out or a SCART cable? If you used a SCART, try the RF out and see if that looks right. If it does, you've probably got a loose/bent/broken pin in your 23-pin video port. If it also looks like blue is missing, it might be a dried up capacitor or poor solder joint somewhere in the video output.
Either way, I don't think it's anything TOO major, if the machine is otherwise behaving properly.
