Lionel No.4 in yellow. A color that often known as orange is called, in this instance, yellow by the Lionel Corporation. This month I will concentrate on pre-World War II production items in orange. This locomotive was also produced in grey. The No.4 Bild-a-Loco features a manual reverse motor designed to be easily disassembled with a screw driver. The locomotive was also produced as the No. 4U. The No. 4U consisted of the unassembled locomotive and track.