A passive reflective device provides a warning or message visible when the intensity of light incident on the device exceeds a preselected minimum intensity or threshold value. The device includes a display, in the form of statements, pictographs, or images, with an appearance which is altered in color or pattern when impinged upon by light with an intensity greater than the threshold value and viewed by a viewer in front of the device. The device can be used as a sign or stationary display, such as a road sign, or it can be mounted on or in a front vehicle facing behind the vehicle such that the display is visible from behind the vehicle by someone who is within a preselected range of angles. The device can be mounted on the bumper or body of the vehicle, and the display can provide information, such as a visible warning to the driver of the following vehicle that his or her lights are shining so brightly on the front vehicle so as to cause the driver of the front vehicle to become uncomfortable, distracted, and/or temporary blind due to reflections of the following vehicle's headlights in the front vehicle's rear view mirror or mirrors. The device may have several appearances which change as the light intensity progressively exceeds several corresponding threshold intensities.