I've seen this problem with both of my Hikvisions, but I don't know what causes it. I tried correcting it in the camera settings, but only ended up making things worse. I'm not experiencing the violet-magenta shift at the moment. My guess is that incident light outside our visible spectrum, e.g UV and/or IR, aren't filtered sufficiently by lens coatings to prevent them from contributing to the camera's auto-exposure algorithms, i.e. white balance. When my pavement (concrete and asphalt) is warm compared to ambient temperature it takes on a magenta cast (IR). Similarly, at times the sky can acquire a like hue when it's overcast (IR again or UV?). It doesn't seem to be as prominent on clear days, hence my guess. Given that the Hikvisions have an IR mode, I'm betting that IR is where the problem lies and that there's no easy fix.
The Hikvisions are designed for surveillance, and exact color rendition under all conditions isn't their goal. Overall, I'm very pleased with their performance.
