Everything you never knew you wanted to know about the Mercury Project
Mercury spacecraft colors and painting
From RixWiki
Posigrade rocket nozzles
Many modelers paint the posigrade rocket system nozzles red, since several model kit instructions call for that. However, this is incorrect for most if not all of the Mercury spacecraft. These nozzles were typically a dull aluminum color. For photos of actual posigrade nozzles, see the article on the posigrade rocket system
Outer Surface Finishing
Many parts of the outside of the spacecraft were not painted, but were the result of the raw materials or non-paint metal finishing techniques.
Shingle Color
Two types of shingles were used, Rene 41 shingles were used on the conical section, while the shingles on the recovery section where made of beryllium
While I haven't been able to find descriptions of the processes used for finishing in Project Mercury Documentation, there is a good description of the processes used for the Gemini spacecraft which was of similar construction and appearance. The following is a excerpt from the Gemini press kit which is on John Duncan's site at http://www.apollosaturn.com/geminiNR/sec12.htm
Manned spacecraft fabrication techniques developed at McDonnell for the Mercury Spacecraft are being extensively applied in the Gemini program. Weight limitations combined with heat resistance, air load, and acoustic requirements have necessitated improved fabrication practices and have placed even greater demands on assembly techniques.
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The Rene 41 shingles on the side of the reentry module are heat oxidized to provide a stable adherent, high temperature resistant high emittance surface finish. The beryllium shingles are chemically oxidized to provide a high emittance surface. An air curing silicate bonded black ceramic coating that has a significant degree of toughness at room temperature, good thermal shock resistance, and will withstand temperatures as high as 2300 degrees is used to repair any scratched or damaged areas that may affect the surface of the shingles prior to launch.
