Uncheck Document > C/C++ Options... > Color Coding > Langauge > Preprocessing keywords can appear anywhere
This has an undesirable interaction with inactive code regions coloring. Should not be a problem because C++ preprocessing can't just be anywhere, it has to be the first non-blank character.
I'll check into the interaction, because it should not break the normal case for coloring inactive code, but that fix would have to go in the next release, not hot-fixable.