Light scattering in sulfur colloids
There are a number of different effects:


Rayleigh scattering is the predominant effect for the tiniest particles, much smaller than the wavelength of light, i.e. before they've coalesced. It is dependent on the fourth (!) power of the frequency of the radiation, so short wavelength light is scattered toward the eye. Looking through the colloidal mixture, it should look redder.
Tyndall scattering applies to larger colloidal particles, and it too is dependent on the fourth power of the frequency of the radiation and preferentially scatter bluer light, so the yellow of the sulfur would be less apparent.
Finally, particles coalesce and scattering becomes less important than reflection from the larger particles.
Perhaps sulfur nano-particles behave a bit differently from bulk material due either to quantum effects or to surface effects. See Elemental Sulfur Nanoparticle Coarsening... If someone has experience with nanoscale sulfur, please feel free to comment or edit this.