Warbonnet is a term for a famous color scheme used by Atchison, Topeka and Santa Fe Railway. First popularized in red and silver on passenger units, variants of the scheme have been used. Starting in 1972, freight engines began using a blue and yellow version, often called "bluebonnet" or "yellowbonnet" by railfans. After the advent of Amtrak, some red-and-silver engines had the red replaced with yellow or blue. These engines were also known as "yellowbonnets" and "bluebonnets". In the late 1980s, the red and silver scheme returned, now on freight engines that were part of the "Super Fleet". The yellow pinstripe seen in the illustration was not applied to all warbonnet-scheme engines.
The scheme is arguably one of the most famous paint schemes ever applied to a locomotive, as it has been popularized (by Lionel and others), ever since first deployed in the 1930s on the Super Chief, an extra fare Named Train between Chicago, IL and Los Angeles, CA.
The warbonnet is well known to LEGO trains modelers as it is the color scheme used by set Santa Fe Super Chief (10020), and many fans have done models in warbonnet paint. The image shown is that of a gas electric railcar or doodlebug model of M105 by Larry Pieniazek.