The color of a surface is determined by tracking the position of the
surface using grayscale image sensing and then using captured grayscale
image information, position information, and grayscale-to-color
conversion information to determine color. In one embodiment, the
technique requires establishing grayscale-to-color conversion information
and a relationship between position and the grayscale-to-color conversion
information. A calibration pattern is printed on a piece of paper and the
surface of the paper is illuminated. Grayscale image information and
position information related to the surface is generated in response to
the illumination. Color-specific portions of the grayscale-to-color
conversion information that are to be used in color determination are
selected based on the position information. Grayscale image information
related to the calibration pattern is then compared to the selected
color-specific portions of the grayscale-to-color conversion information
to determine the color of the calibration pattern.