The emissivity of a gray body is constant but is considered to be less than 1. Since the black hole is considered near perfect black body but not a perfect black body its emissivity will be less than one hence can it be considered as a gray body?
A quote from this paper:
At the precise location of the event horizonthe Hawking radiation is blackbody radiation. However, this radiation still has to traverse a non–trivial,curved spacetime geometry before it eventually reaches an observer and is detected (e.g., an observerlocated at asymptotic infinity in an asymptotically flat spacetime). The surrounding spacetime thus worksas a potential barrier for the radiation, giving a deviationfrom the blackbody radiation spectrum as seen byan asymptotic observer. The relative factor between the asymptotic radiation spectrum and the spectrumof blackbody radiation is dubbed the greybody factor.