Shades On Classic US

anyone on the forum an expert on shades of classic us stamps. I am particularly interested in information regarding the 24 cent 1861s and 1863's 70-70d and 78-78c as well as the shades of the 5 cent 1861. Has anyone ever seen an unused copy of scott 67b---olive yellow. Scott has it unlisted as unused, but this seems illogical as known used copies certainly exist. Stands to reason that there should also be unused out there as well. Even the 78c has had a few unused copies surface.

I am not an expert on color varities but a handy way to determine various colors is too acquire many inexpensive stamps such as the 1922 definitive series , and mount various colors side by side on a page to contrast the shades .

If a used/unused copy is not known to exist, Scott will leave the price spot completely blank (not even a dash). This is true even if a used/unused copy theoretically should exist.

When a copy is known to exist, but there is insufficient information to provide a catalog price, Scott will put a dash.