1. A method comprising: staining a tissue with both a test biomarker and a known stain; acquiring a digital image of the stained tissue; identifying a first cell component region that is stained by the known stain, wherein the first cell component region corresponds to a first cell component; identifying a second cell component region using the first cell component region, wherein the second cell component region corresponds to a second cell component; determining a stained proportion of pixels within the second cell component region whose colors fall within a selected color range, wherein the test biomarker stains tissue to have a color that falls within the selected color range; identifying the test biomarker as a stain for the second cell component if the stained proportion of pixels whose colors fall within the selected color range exceeds a predetermined proportion; and displaying on a graphical user interface an indication whether the test biomarker is a stain for the second cell component.