Comparison of the observed and AS distributions for real stars (top panels) and ASs (bottom panels). Black points indicate the sources located between the two green fiducial lines in Fig. 1f, whereas grey points mark the remaining stars. (a)-(d): m_F606W versus m_F606W − m_F150W2 CMDs. The red line represents the fiducial sequence used to inject ASs. (b)-(e): Verticalised CMDs based on the fiducial sequence. Δ_{F606W − F150W2} represents the verticalised colour. (c)-(f): Histograms of the colour distribution for sources within the cyan-shaded regions of the verticalised CMDs. The red curves show Gaussian fits, with the dispersion (σ) computed from the 68.27th percentile of the distributions. The corresponding σ values are indicated in each panel.