All I can think of is either damage to the chip/chipset that *sends* the signals to the video connector, the traces between them, or bad solder joints on the connector itself.
Having a bad pin on a DB15 often causes color shifts because they send the color signal to the monitor. Usually that would be an emphasis on R, G, or B or a lack of one of them, but it's not beyond the realm of possibility for it to result in a yellowish tint.
Also, while this is unlikely, if you have a strangely compatible MAC PCI card in a PC, the older PCI Macs generally synced on the green signal, and PCs didn't. In my experience that results in a sort of teal screen, though. This shouldn't work at all, but I just took a Matrox Millenium out of a Mac and it worked on a PC (it might be a PC card in the first place, but it's hard to tell from the markings).