I have a recording of an old VHS that for 60% of the picture has correct color (if only faded but it is easily fixed with more saturation and hue and such). However, the top part of the video would periodically discolor to a more purple/magenta color and at random intervals.

I have attached a sample picture, I have been able to use multiple masks and color matching to lessen the discoloring though you can still tell in many scenes and can see some artifacting going on as the masks swap colors around. I am wondering if there is an easier way to have the masks pick out the colors like in color matching but then perhaps just sliding the hue and saturation so that the underlying color could be found rather than using a dozen or more color matching replacements?

And yes I did try to clean up the VHS as much as I could and did get a lot of improvement but the top of the video continued to be discolored so I believe it's a degradation of the tape itself.