(This question is a duplicate of What is the physical origin of scintillation?) The answer is in the link below. Short version: Refractive gradients in the mixed atmosphere, thousands of meters above the surface, are far too small to act as lenses and prisms, and scintillation is not a geometric optics phenomenon. It results from interference effects of plane-wave light (spatially coherent light, like starlight or laser light) as the wavefront is distorted by tiny refractive gradients associated with Kolmogorov turbulence. This accounts for both the intensity and color fluctuations seen by eye, and also explains why the larger planets, whose light is far from coherent, do not scintillate. Little's paper anticipates by a decade the works of Kolmogorov, Tatarski and Rytov. It also anticipates speckle, seen in larger apertures, where the distorted wavefront breaks up the Airy disc into tiny pieces that fluctuate on millisecond time scales.
Enchanted Learning, like other simple refraction/dispersion explanations, is simply wrong. Little's paper requires some understanding of Fresnel diffraction, but it's well worth the read.