Here's a bit of "yellow bonnet" trivia for you:
Every prototype rednose F-unit started as a "yellow bonnet" - well, sort of.
I saw several of them painted in the San Bernardino backshop. The first step was to mask off the entire warbonnet and apply primer. Next, black was sprayed along the edge of the stripe, in the area of the "cigar band", and up the nose to the center windshield post. The black nose emblem outline and lettering, the lower frame stripe, the engine number at the rear of the warbonnet, and the black stripe on the warbonnet were then masked and the entire warbonnet inside of the black stripes was painted yellow. Next, the yellow striping and nose decoration were masked, and red was applied. Last -- after the red was covered with a tarp -- came the aluminum paint on the louvered panels, end bulkhead, engine room side doors, fuel tank, trucks, pilot, steps, and the roof. In the case of early F3's 16 through 21, this would have included a larger aluminum area, as they did not have stainless steel side panels.
The classic freight F-unit scheme also was painted black for the lettering on the nose emblem, then entirely yellow, masked, and then painted blue over the yellow (all lacquer). Last was the black enamel on the pilot, fuel tank, and trucks.