My printer/driver can only produce grayscale output. So it doesn matter what value COLOR has, right?
Wrong. For examples, a2ps uses colors to render headers, do pretty- printing etc. These colors look different on a grayscale printer than the gray levels used when COLOR=mono is set. Additionally, some converters use special algorithms when they are told to produce grayscale output; this might improve the result. They usually run faster in this mode, as well.
