Zoomed-in optical and X-ray light curves where optical flares are essentially simultaneous with X-ray flares (optical is shown in red, soft X-ray (3–10 keV) in orange, hard X-ray (20–80 keV for ISGRI, or 10–79 keV for NuSTAR) in green, and very hard X-ray (80–200 keV) in dark blue). For each subplot, the HRs (HR1 is plotted in orange, and HR2 in dark blue) and the DCFs (optical ACF is shown in red, optical/soft X-ray DCF in orange, optical/hard X-ray DCF in green, and optical/very hard X-ray in dark blue) are shown below the light curves. The variation in behaviour is discussed in the text.