There was definitely a B unit there in 1939:
The Winter 2018 Classic Trains has a two page color photo spread of these units as they appeared in 1939. They were white or slightly off-white (ala CB&Q's "aluminum???") Top two stripes are red, bottom two silver or stainless steel.
It would seem reasonable that the main portion of the body remained the same "white" color and the top painted red for the 1940 display along with the addition of the black nose wings.
The locomotive also appears to be further back toward the pavilion in 1940 and has the glass sides. I would reason the B unit was removed from the 1940 display.
Rusty