IXPE, NuSTAR, and NICER light curves of GX 3+1 (count s⁻¹). The second panel shows the IXPE hardness ratio (5–8 keV/3–5 keV). The fourth panel shows the NuSTAR hard color (10–20 keV/6–10 keV). Empty black circles denote the NuSTAR points that are not simultaneous with the IXPE observation. The gray regions correspond to the time intervals during which the source moves in the UB branch. For IXPE and NuSTAR, we considered time bins of 200 s, whereas for NICER we opted for 50 s bins.