Top: Fractional rms vs hardness ratio calculated as the BAT flux/MAXI flux and the optical fluxes obtained at the Al Sadeem Observatory in the g′, V, and R bands (blue, green, and red points, respectively). Linear fits are represented with colour-coded dashed lines. Results of the fits are reported in Table 1. Bottom: Fractional rms vs hardness ratio calculated as the 2-10 keV Swift/XRT flux / the 0.5-2 keV Swift/XRT flux and the optical fluxes obtained at the Al Sadeem Observatory in the g′, V, and R bands. Results of the fits are reported in Table 2.