Edit - I updated this first post on 8/2/10 to reflect the additional info collected so far. Thanks for the help and feel free to offer further corrections or info. On another site someone was just asking about the correct color for the motor in a truck kit, this got me thinking it is a pretty common question and since there is a fairly limited number of truck engines available in kits or resin it could be handy to make up a list of the colors so we have the info in one place. Allis Chalmers - Plum Crazy Purple Caterpillar 3406 - New Cat Yellow 3208 - New Cat Yellow Cummins NHC250 - Cummins Beige NTA370 - Cummins Beige NTC350 - Cummins Beige N14 - Black (may have red valve covers) V-903 - Dark grey or Black Detroit Diesel Series 60 - DD Alpine Green 6-71 - DD Alpiine Green 8V71 - DD Alpine Green 12V71 - DD Alpine Green or Silver 16V71 - DD Alpine Green 8V92 - Silver Chevrolet 1940s to late 1950s - Medium grey Late 1950s to 1963 I-6 engines Chevrolet engine blue, V-8 Chevrolet engine red (orange) Ford Ford 331 Flathead truck engine - Dark Spruce Green OHV 1954 to 1961 - Red 534SD - Ford Blue GMC GMC 1940s - Avacado GMC late 1940s to early 1950s Dark Green GMC 1950s Crimson Red GMC 1960s V-6 Alpine Green, V-8 Red Turbine - Red International V-800 - Metallic blue Mack - Pre 1990 gold, Post 1990 grey, or blue / grey if equipped with an intercooler ENDT675 ENDT676 ENDT865 4cyl (Mack AC) - medium grey Super tip turbine - red Exceptions, some truck manufacturer's use their own colors instead of the engine builders color AutoCar - White through 1968-69 then manufacturer color Ford - Black until 1965, Ford Blue until 1982, Ford Corporate Grey Diamond Reo - Red Peterbilt - White through 1984 then engine manufacturer color Kenworth - White through 1975 then engine manufacturer color Might as well include the available paints as well Krylon New Cat Yellow Old Cat Yellow (I believe Caterpiller changed to the new yellow in the 1950's) Duplicolor Detroit Diesel Alpine Green Ford Blue Fleetrite (available at International dealers) Cummins Beige DT466 Blue Testors Model Master offers many factory engine colors. Suggestions for close matches with non-factory paints IH V-800 - Testors Model Master Lacquer #28150 metallic 1969 Ford Acapulco blue IH V-800 - Tamiya #TS19 Metallic blue Diamond Reo / Mack - Testors Model Master #52709 Boyd Red DD Alpine Green - Testors Model Master Acryl #4774 RLM 25, Polly Scale #505270 British Interior Grey Green AC Mack Grey - Model Master #1725 Neutral grey, Model Master Acryl #4757 Neutral grey