They were special Red, White & Blue painted trains that visited manufacturers across the U.S. in 1941 to encourage and locate war suppliers and help with war build up .
Thanks to C Buss for bringing it to my attention. She says "My father, George k. Culbertson, was with the signal corps display on the Defense Special Train going west in 1941, starting in Washington, D.C., and stopping in Denver, Seattle, Spokane, Los Angeles, San Diego, San Antonio

This is what I found about it so far and would love to know more !

Defense Special Train Articles

War Mobilization and the Use of Small Manufacturers

762 nd RSB Brief History

Yankee Boomer 1945 Photo v2... by Nancy

rdgrrmag1045

3rd shingler by cunningb

Troops and Trains rolls into Strasburg

Click to enlarge or right click to save to your computer.
Thanks very much to Bill Varner !

724th Railway Operating Battalion Roster by cunningb

Thanks to Steve Newton for this great photo. This is Company A of the 728th. It was a L&N railroad sponsored company. His Dad, Roy K. Newton served in this unit. (He is standing on the back row, 8th person from the left.)

Great photos of Roy Newton !

This great history of the 735th Railway Operating Battalion and service of Carl Vernoy, thanks to his daughter Mary for sharing it. Thanks to:
Mary Vernoy
ATC(AW/NAC)
USNR-RET

735ROB Comb'd Hist by cunningb

Her dad's discharge papers :

750th Wilton