An imaging system for a vehicle includes an imaging sensor (12) and a display device (15) for displaying images representative of image data captured by the imaging sensor. The imaging sensor (12) has a rearward field of view when mounted at the vehicle. The imaging system generates a plurality of graphic overlays (130a, 130b, 130c) on the displayed images to enhance the driver's cognitive awareness of an object rearward of the vehicle. The graphic overlays comprises a plurality of graphic overlay segments. The graphic overlay segments convey three dimensional information to a person viewing the displayed images and the graphic overlays. The imaging system may adjust at least one of a color, an intensity and a rate of flashing of at least one of the plurality of graphic overlay segments in response to an object being detected rearward of the vehicle and within a distance threshold.