Is it possible to stain over terrazo floors?
I have never seen it done but it makes sense to me that it could be done to some degree.
I would think the floors would first have to be stripped then sanded(screened).
I wouldn't know what stain to use but I would think the everyday acid stains used for concrete would work.
Try this website. Gaye is a pioneer in acid staining concrete and if anyone would know how to do it she certainly would. The website has a forum like this one. Sign in there and ask your questions.