Just a quick note that a very helpful fellow on the Apple IIoz mailing list pointed out that there are two variable resistors on the top of the PAL card that can be adjusted to tweak the video output. (Honestly, I mistook them for Foil Film Capacitors as they were blue blocks on the top edge. It was only when I looked at them more closely that I noticed they had a tiny embedded screw-head)
A quick setup later and a bit of fiddling and I had perfect stable colour from the Apple IIeuroplus.
I then decided to see if I could improve the picture on the Apple IIe using the same approach (The IIe PAL basically just has the PAL card integrated) and it was just as simple! Find the two variable resistors and gently dial in the picture.
Now I have TWO Apple IIs that are fully set up with Disk Drives. Time to play some old Ultima V. Now where was that Magic Carpet again?