This thread is getting out of control as far as answering Meric42's question. I apologize that I cannot answer the original question either, but wanted to add about the '55 Mercury engine colors. In '55, the Mercury Montclair 292 (198 HP) was all the same color (Yellow). The 188 HP 292 that came in other models was the same, except had cream valve colors. Both engines had red letters on the valve covers.
The engine in Raceron1120's '56 Fairlane has colors from different years and makes. Gold block and heads is '56 Mercury 312, cream valve covers are '55 Mercury 188 HP 292 and red intake is '55 thru '57 Ford and Thunderbird 272, 292 and 312.
Sal