A display device and a display method are provided. The display device includes: a first substrate; a light guide plate opposite to the first substrate; a grating layer including gratings, on the light guide plate and at a side of the light guide plate facing towards the first substrate, wherein each grating corresponds to one pixel; and a light source at a lateral surface of the light guide plate parallel to a light emergent direction of the display device, wherein the light source includes monochromatic light emitting components and an optical component, lights of different colors emitted by the monochromatic light emitting components are incident into, via the optical component, the light guide plate at different incident angles and are emergent from the gratings, and the incident angles are greater than a total reflection angle of the light guide plate.