Display backlight structures may provide backlight illumination that passes through display layers in the display. Light-emitting diodes may emit blue light into an edge of a light guide plate. Optical films may overlap the light guide plate. The optical films may include a quantum dot enhancement film. A peripheral strip of yellow reflector or other light control structures may be incorporated into the backlight structures to reduce blue edge effects. The light control structures may have features with a spatially varying density, may be formed from quantum dot enhancement film, or may be formed form other structures. The light control structures may be formed on the surfaces of the optical films, on a reflective layer under the light guide plate, or on a surface of a mold frame or other structure that lies in a plane parallel to the plane of the light guide plate.