Frequency and fractional rms amplitude of the Type-C (red) and Type-B (blue) QPOs as a function of the hardness ratio. Top panel: QPO frequency. Circles represent the rising phase of the LE light curve, while stars represent the decay phase. Vertical lines mark the representative Insight-HXMT observations in Table 1. Notably, the Type-C QPO is not detected at the peak of the flare, which corresponds to the minimum hardness ratio. Middle panel: Fractional rms amplitude in the LE band. Bottom panel: Fractional rms amplitude in the HE band. The arrows indicate an upper limit.