Reading Color; Reading Monochrome - Epson ES-1000C Reference Manual

Reading color

By illuminating the document with three lights, red (R), green (G),
and blue (B), the scanner can analyze and separate a document's three
color components. The computer can then overlay this color-separated
data to produce full-color images.

Reading monochrome

Even though you have a color scanner, you can still read your documents
as monochrome. Color scanners can read documents as monochrome in
two ways:
Treat all the data on the page as the same color. This method uses
all the light sources, and is fine if you plan to print data in black
and white only.
Specify one color (R, G, or B) as a dropout color. This method
uses only one light source and reads all data except for the color
specified.
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Overview