With the usual disclaimer about color issues associated with scanning and display, there are two color charts of US stationery available on this page on Stamp Smarter.
https://stampsmarter.org/learning/S...Posters.htmlOpen the drawer for 1900-1930.
This were scanned on an uncalibrated Epson Expression 12000XL Photo Scanner at my local library. This should at least provide some relative color comparisons.
Mike