The display itself is green, i.e. its pixels output different shades of green. So it isn't just a black-and-white display that is shaded green by an overlay, if that's what you mean.
The Game Boy Pocket did have an actual black-and-white display though. The sprites themselves aren't necessarily black-and-white, or green, they're just varying shades of luminance (their pixel values are stored as numbers between 0-3). What colours you saw depended on what kind of screen that luminance is displayed on.
The Game Boy Pocket did have an actual black-and-white display though. The sprites themselves aren't necessarily black-and-white, or green, they're just varying shades of luminance (their pixel values are stored as numbers between 0-3). What colours you saw depended on what kind of screen that luminance is displayed on.