A probability impact diagram chart is an X,Y chart, in this case the probability is on the Y axis, with 5 steps, very low, low, medium, high and very high. The impact is on the x axis with the same 5 steps. The chart is colour coded. With a green cell for very low / very low, yellow cells for very low / low and low / low combinations, amber for very low / medium, low / medium and medium / medium combinations, red for very low / high, low /high / medium / high and high / high combinations and dark red for very low / very high, low / very high, medium / very high, high / very high and very high / very high combinations.