Left: Normalized accretion disc transfer functions Ψ(τ|λ) for the four photometric bands: 4858 Å (blue), 5315 Å (green), 6043 Å (orange), and 7705 Å (red). As predicted by standard thin-disc (SS73) and lamp-post models, the transfer functions broaden with increasing wavelength. Longer-wavelength emission arises from larger radii, resulting in longer time delays due to the greater light travel distance. Right: Observed normalized continuum light curves (points with error bars) compared with model predictions. Dashed lines show the results from a single-band modelling approach, in which a latent signal is inferred independently for each filter. Solid black lines show the model light curves computed from the joint GPCC-inferred latent signal, convolved with the corresponding transfer functions. The shaded regions represent the 1σ uncertainties propagated through the model scaling process; see Appendix C.1 for details.