Gamma ray burst afterglows can be identified in single epoch observations using three or more optical filters .
This method relies on color measurements to distinguish the power law spectrum of an afterglow from the curved spectra of stars .
Observations in a fourth filter will further distinguish between afterglows and most galaxies up to redshifts z \approx 1 .
Many afterglows can also be identified with fewer filters using ultraviolet excess , infrared excess , or Lyman break techniques .
By allowing faster identification of gamma ray burst afterglows , these color methods will increase the fraction of bursts for which optical spectroscopy and other narrow-field observations can be obtained .
Because quasar colors can match those of afterglows , the maximum error box size where an unambiguous identification can be expected is set by the flux limit of the afterglow search and the quasar number-flux relation .
For currently typical error boxes ( 10 – 100 square arcminutes ) , little contamination is expected at magnitudes R \lesssim 21.5 \pm 0.5 .
Archival data demonstrates that the afterglow of GRB 000301C could have been identified using this method .
In addition to finding gamma ray burst counterparts , this method will have applications in “ orphan afterglow ” searches used to constrain gamma ray burst collimation .