Have been looking at fairly low-end internal doors - with glazing.
Many seem to have plastic glazing frames and dividers. In white with nicely placed holes (probably left from nailing them in place).
Asked, and were told that they were not paintable. (That is, the door is, but the glazing surrounds are not.) So absolutely stuck with that white finish forever even if you paint the rest red, blue, or even delicate pink.
Please tell me that this isn't that case. That the manufacturers have used a paintable plastic.