Histograms of Δr/ Δ(u − r) amplitude ratios are compared for WTTS (blue), all CTTS (magenta), accretion-burst-dominated CTTS (orange), and circumstellar extinction-dominated CTTS (green). Histogram bars for bursters and the variable extinction group are shifted by −0.025 and 0.025, respectively, relative to the bin center and are placed side by side for a better visual comparison of the overall distributions. The slope predicted by the interstellar extinction law is shown as a black dashed line.