  A combined experimental and theoretical investigation of time- and
alignment-dependent propagation of light in an ultracold atomic gas of atomic
$^{85}$Rb is reported. Coherences among the scattering amplitudes for light
scattering off excited hyperfine levels produce strong variations of the light
polarization in the vicinity of atomic resonance. Measurements are in excellent
agreement with Monte-Carlo simulations of the multiple scattering process.
