One possibility is that the film is upside down. You get red images when you expose through the base.
On the other hand, it's normal to get a yellow-red image indoors under tungsten light with daylight film, and it could be that the long exposure with the pinhole camera is causing a color shift due to reciprocity law failure, so there could be multiple effects going on.
How are you printing these? Another possibility is that the colors are correctable, but if you're giving the film to a lab, their automated machinery can't deal with the negs.