I found the actual law regarding the copying of the certificate. It does not say anything about color copying or some such. I suspect that is more of a recommendation rather than actual regulation.
http://www.law.cornell.edu/uscode/html/uscode18/usc_sec_18_00001426----000-.html
1426. Reproduction of naturalization or citizenship papers
(a) Whoever falsely makes, forges, alters or counterfeits any oath, notice, affidavit, certificate of arrival, declaration of intention, certificate or documentary evidence of naturalization or citizenship or any order, record, signature, paper or proceeding or any copy thereof, required or authorized by any law relating to naturalization or citizenship or registry of aliens; or
(b) Whoever utters, sells, disposes of or uses as true or genuine, any false, forged, altered, antedated or counterfeited oath, notice, affidavit, certificate of arrival, declaration of intention to become a citizen, certificate or documentary evidence of naturalization or citizenship, or any order, record, signature or other instrument, paper or proceeding required or authorized by any law relating to naturalization or citizenship or registry of aliens, or any copy thereof, knowing the same to be false, forged, altered, antedated or counterfeited; or
(c) Whoever, with intent unlawfully to use the same, possesses any false, forged, altered, antedated or counterfeited certificate of arrival, declaration of intention to become a citizen, certificate or documentary evidence of naturalization or citizenship purporting to have been issued under any law of the United States, or copy thereof, knowing the same to be false, forged, altered, antedated or counterfeited; or
(d) Whoever, without lawful authority, engraves or possesses, sells or brings into the United States any plate in the likeness or similitude of any plate designed, for the printing of a declaration of intention, or certificate or documentary evidence of naturalization or citizenship; or
(e) Whoever, without lawful authority, brings into the United States any document printed therefrom; or
(f) Whoever, without lawful authority, possesses any blank certificate of arrival, blank declaration of intention or blank certificate of naturalization or citizenship provided by the Immigration and Naturalization Service, with intent unlawfully to use the same; or
(g) Whoever, with intent unlawfully to use the same, possesses a distinctive paper adopted by the proper officer or agency of the United States for the printing or engraving of a declaration of intention to become a citizen, or certificate of naturalization or certificate of citizenship; or
(h) Whoever, without lawful authority, prints, photographs, makes or executes any print or impression in the likeness of a certificate of arrival, declaration of intention to become a citizen, or certificate of naturalization or citizenship, or any part thereof