Scott 357 Bluish From Hartford?

This 1c Franklin looks a bit brown, but perhaps it's because of the bluish rag paper? Postmark 1909 checks out, but it's not from D.C.

Do these stamps carry much of a premium?

Here is another one. The postcard paper is bright white and generally very clean, so I don't see how only the stamp turned brownish.

Neither stamp are #357, Bluish Paper. Judging the stamp paper "coloring" by comparing to the post card probably isn't a factor you should use. I doubt they are of the same composition. Below is from the Harmer Inc. sale of the Georgetown Collection of W/Fs in 2006. This is not to say this is want you have; only that there has been a paper variety cert'ed. other than the Bluish Paper.
There are factor, such as storage and exposure to light etc. that have an effect on how a stamp "ages" over the 100yrs. plus that this issue has been around. These are probably toned #331s. Others may have a better insight as to what you have and the conditions they are in. This "brownish" paper variety may or may not still be recognized today.

I thought toned when I saw them.
Don

There are plenty of covers like this. While maybe they could be largely all brown papers, I would doubt it.

The stamps were likely just badly stored before being used. "Badly" may be wrong as most people had coal fired stoves emitting sulfur compounds (converting to sulfuric acid) and probably other acidic elements that would age/brown paper. They might not have been this bad in 1909, but acidic elements would age the stamps faster than the cards over time. Besides, the card backs are surfaced with papers containing kaolin or somesuch to be white and have stayed white over time. What do the front side of the cards look like? Browned/toned?