I have a newly half-unboxed Catrine here -- the Scaris version, if that matters -- and it is very much a pure white. I held a white envelope from the junk-mail pile up against the plastic, and the paper was slightly brighter than the plastic... but the plastic is still not something I'd call gray by any stretch. Before the comparison, I was leaning toward saying it had a purple tint, but that's probably only because of the purple hair, the purple clothes, the purple backdrop, etc.
UPDATE: OK, this is the darnedest thing. I just took a closer look at my Catrine, and it's now apparent that her lower legs are a slightly different tone than her upper legs. They even seem to have a different degree of luster. Each piece is solid (no gradation of color), but they're definitely different. Weird! Also, I was looking around for something common to compare the color to (which is what led me to take the closer look), and the white of the upper legs is definitely comparable to the white plastic of a Wii game case.
This photo (with no flash) shows the difference. Everything appears slightly darker than it is because of the camera and mediocre lighting, but you can see the difference in tone (and also how each compares to a Wii game case). All other parts (head, arms, tail, torso) seem to be the same tone as the upper legs; it's only the lower legs that differ. Weird.