The Flipper Zero's screen is transflective, I suspect this one is the same. While this technology is possible on larger color displays, it is more common to find these manufactured as small grey-scale screens. They're ideal for battery operated devices because of their low power requirements -- they are legible with the backlight entirely off as long as there is light in the room.
Grayscale displays have no subpixels (or just one, depends how you view it) which should allow for more light from the backlight to pass through compared to a color display, thus reducing energy needs for a given brightness.
Remember these?:
https://m.media-amazon.com/images/I/81sQxjJBn1L._AC_.jpg