A satellite probe that is set to flash a blue light every second is fired slightly off the horizon. As it nears the horizon, you notice its beeps slow down and the color changes from blue to red. The slowing of the beeps is paused because the gravity has caused time to slow down or dilate. As a result of the time dilation, the blue light that the probe flashed out turned red near the horizon. Our eyes see blue light as waves with high frequency. When time slows down the reception of these waves, the light waves becomes low frequency which is the color red. As the probe reaches the event horizon, the gravitational red shift becomes infinite, and the red flash remains frozen on the horizon.