I have read in 445 Intoduction Papers, that the new series of tractors (some refer as constelation Series) were to be painted a new color, to be known as "Power Yellow" It is NOT Prairies Gold #2. PG2 was used from about 1948 thu the ZB, UB GB, etc. However, for Simplicity or error some MM Repair Catalogs continued to refer to Prairie Gold, even thru the White years in the 1960's. Hence so many MM's being repainted wrong colors in the 1960's & 1970's.
Also back then, MM bought Paint from various suppliers, so there were many "slight differences" in paint, but we as collectors & Historians must call them by their correct names, as to have the historical record documented correctly.
White changed to "Energy Yellow"