Troubleshooting a Genesis Model II

[Legion]

I turned on my Genesis Model II yesterday and the picture output is heavily tinted yellow. Basically anything that should be white is yellow. I tried the composite output and it looks fine. But on RGB it's yellow. So it looks like the blue channel isn't getting through. It's also being really intermittent with games starting up. It powers on to a blank screen a lot. I have to try multiple times to get the game to come up. The two issues could be unrelated.

What makes this strange is that everything was perfectly fine 2 weeks ago. Games booted up fine, color was great.

[Legion]

I took it apart and cleaned the board. It wasn't too bad, just some dust. I cleaned the cartridge slot too. That seems to have fixed the intermittent problem. But the yellow is still there. I've confirmed there is no blue signal getting through. So it could be the cable or the genesis. I don't have another model II to test it with.

[Legion]

I lied. I do have another genesis. Same thing happens. So it's the cable. Checked the cable for continuity, continuity is there. Took cable apart, SCART end wasn't seated correctly leading to intermittent connection on blue channel. Reseated. Fixed.