Here is an interesting paper, pointing out that multispectrum light "packets" do redshift over distance, because the higher frequencies dissipate faster;

http://fqxi.org/data/forum-attachments/2008CChristov_WaveMotion_45_154_EvolutionWavePackets.pdf

Yet this would mean we are sampling a wave front, not seeing individual photons that traveled billions of light years. Which would imply the quantification of light is an artifact of absorption and measurement, rather than fundamental to the light itself.