I occasionally get some weird colors in PM when colormatch is turned on.
They are totally overstaurated. I have some screenshots.
Colormatch off looks like this

On looks like this

Addn a screenshot from PS :

It happens randomly, mostly ropening contactsheet after conversion of files.
Quitting and relaunching makes it go away - most of the time.
I recall vaguely having read somewhere in another forum about deleting a plist file, but I can't remember which one

PB G4 15" 1,5Gb RAM 10.4.9
-Søren