Under some circumstances, stars can twinkle with different colors. There is no physically plausible explanation for a multi-colored screen in the atmosphere, and even though the refractive index of the atmosphere is somewhat wavelength
dependent, this effect, roughly a 2% effect across the visible band, is too weak to cause the lens-like structures to
directly produce a visible color effect. For much the same reason, the shadow pattern at the bottom of a swimming
pool on a sunny day shows no apparent color. However, a related, indirect consequence of dispersion can explain this
phenomenon