This chart is the same as U.S. Real Home PE-like Ratio (with SD) - Monthly except that the the horizontal lines are removed and the index values colored to denote them as over/undervalued when they are more than one standard deviation above/below the average and extremely over/undervalued when they are more than two standard deviations above/below the average.
mccormick-charts.com: U.S. Real Home PE-like Ratio (with SD) - Monthly
external: Case Shiller Index, standard deviation