HP Color LaserJet CP1515n - Prints Magenta pages

[MindrustUK]

I've got a HP Color LaserJet CP1515n that for some reason when printing in color prints Magenta pages. Ie the white part of the page is pink, all other colors seem to be fine. If I force black and white, I get clean prints without issue (no pink on white).

I know little about the workings of printer internals but am competent with most electronics. I'm guessing this is probably a dry capacitor or similar but if anyone could assist me with a few pointers on how to diagnose / repair this, I'd be grateful. Thanks!