It seems that the colors white/yellow in the videosignal is replaced by cyan, or maybe not exist at all.
The Amiga video port is RGB (Red, Green, Blue). If your whites turn Cyan, it means your RED signal is gone.
I'd check the RED pin on your Amiga RF modulator box, and the corresponding pin on the Amiga, itself. It's probably bent/damaged/loose somewhere.
Pin 3 is listed as "Analog Red." This should be the pin to check out.
