WP boxcars were always painted white/black (and in the '40's Aluminum paint that looked white). The feather was never in color. On the paint diagrams, WP called the herald "medallions".
The WP reefers were always painted too, as opposed to that era of SP/UP shields.
Steam tenders and diesels OTOH, had the medallion plates (red/orange feather)
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RJ Dial
Mendocino, CA