Intrinsic colour excess in H − K versus the mass accretion rate. The typical uncertainty for the colour is plotted close to the bottom right corner. Triangles are upper limits for the accretion rates. Crosses represent classical T-Tauri (boldface crosses) and weak T Tauri (normal crosses) stars from Meyer et al. (1997). The best fits are E(H − K)₀ = 1.51( ± 0.26) + 0.12( ± 0.05)  ×  log Ṁ_acc (dashed line, Pearson correlation coefficient 0.50) for HAeBes with Ṁ_acc  >  1.5  ×  10^-7 M_⊙ yr^-1, E(H − K)₀ = 1.26( ± 0.34) + 0.10( ± 0.05)  ×  log Ṁ_acc (dotted line, Pearson correlation coefficient 0.50) for CTTs, and E(H − K)₀ = 1.63( ± 0.17) + 0.15( ± 0.03)  ×  log Ṁ_acc (solid line, Pearson correlation coefficient 0.65) for both HAeBes showing high accretion rates and CTTs.