1 Cent Franklin Paper Question.

I don't think these are "bluish they look more brown to me. Can anyone tell me why the color is so much different than the others I have from the same time. Please and thank you!

It is likely that acid from the postcard has affected the stamp paper. Alternatively, but very unlikely is "dirty water" paper. The former "China clay" paper variety, variously described in multiple ways including "gray paper" was found to contain no Kaolin clay but contained silica from water at the paper mill. It is now called "dirty water" paper. The examples I have seen are either grayish or have a white porcelain look. Because the definition was inconsistent, the variety has no particular identifying features except that the paper color may be whiter or grayer.

Okay. Thank you very much! I'm still new to all of this!