The first spectroscopic observations in 2004 showed that the visible spectrum of Orcus is flat (neutral in color) and featureless, whereas in the near-infrared there were moderately strong water absorption bands at 1.5 and 2.0 μm.
As primeiras observación espectroscópicas feitas no 2004 amosaban o espectro visible de Orcus coma plano (neutro en cor) e sen características rechamantes, mentres que no infravermello próximo existían unhas bandas de absorción de auga moderadamente fortes a 1,5 e 2,0 μm.