Here's a 1920 copy of The Road to Oz in dustjacket. What makes this special for me is the fact that the cover design features a blue background, rather than yellow.
The original Reilly & Britton version of this book only used this lovely cover image on the dustjacket, where it was originally printed with a metallic gold background. The book itself had a stamped cover with a different image. Later R&B printings used this blue background on the jacket.
When the publishers changed to Reilly & Lee, a cover label using the dustjacket art replaced the stamped cover. The earliest R&L copies used a yellow background, but this copy is from the very brief time period (1920) when Reilly & Lee used blue for the background on both the jacket and the cover label, before switching back to yellow for the remaining years.
I've wondered why they would switch back to blue for such a short time period - perhaps they were using up some leftover sheets? I've always preferred the blue to the yellow background.
The Baum family scrapbooks have an example of a printer's proof of this cover with a green background. There is also a blue wash over Dorothy's companions - apparently something that was not pursued in the final product. This rarity was featured on the rear cover of the Autumn 1990 Baum Bugle, and I've always been curious whether the green was a metallic ink, like that which was used in The Emerald City of Oz the following year. If anyone has seen this in person, I'd love to know!
Here's a lineup of the various colors tried and used on The Road to Oz dustjackets. I only have the blue one, and the green one doesn't seem to have been produced to be used, but wouldn't it be fun to have all four colors!