With Harman Direct Positive paper, I sometimes get prints that are pink, rather than white. I never quite figured out what's causing it, but I accidentally found a solution.

Because this paper is fibre based, the instructions recommend washing it for an hour(!) I don't know anybody who actually does this, but a trick we used to use for FB paper in the darkroom was to add some Ilford Washaid or "Hypo Clear" into the wash bath, to neutralise any remaining fixer in the paper and make it more archival more quickly, while saving water.

I happened to have some Sodium Sulphite mixed up (which is the active ingredient in Hypo Clear, and also handy when doing BW Reversal as a clearing bath), so I poured it onto my pink print and it immediately lost the pink colouration, turning a nice neutral Black and White.

Has anyone else struggled with pink prints?