It hit me repeatedly as I would exit the interior of Castle Seaview, so no, this was going on in an exterior, though in the courtyard of Castle Seaview. I walked in and out of the Castle about a dozen times and it was constant in its behavior.
I have Black Screen fix option active in my Bashed Patch already. I had never experienced a Black Screen around the Castle (or inside it) before I activated the colored seasons option. I practically never see Black Screen while playing, anywhere. This may just be a conflict with Castle Seaview and other mods when that option is enabled. I can live with it off.