You know Brad, that's a great question. we're getting ahead of where I'm at on this subject. I've been focussed on the Streamlines and what's correct and haven't gotten into the subtle nuances of the Mainliner and Champion line. I'm really looking forward to getting this all hammered out, and in fact I have had a discussion with Nate about us going through the learning process together. perhaps I should start a thread and invite anyone interested in delving deeper to join the discussions. for now my answer has to be that the Firestone ads do not mention color for that model in that year. The Huffman catalog does list color options but not silver and red. I sadly do not have the Dayton catalog so I not sure what the options were. Silver and red were used by Firestone, but we can't say for sure if this is the case on your bike.
the no head badge thing would be a good indication that it was a big tank bike, but there were Champions built without tanks and I'm not sure about them.
I do have this for you, it's the original paint Front Flex fork on the 1940 Twin-Flex that's coming.