It's more difficult to pin these other speaking figures down as specific founding fathers, but the fact that they look so different from the generic big-nosed men suggests that perhaps they are intended as specific people.

A few suggestions as to who this could be, based on the assumption that whoever it is did not actually have turquoise hair:

John Adams (I think this is most likely.)

Thomas Miffin

George Wythe (although the lack of glasses are a significant factor here.)

Richard Stockton

George Clymer

And I'm even going to leave room for the possibility that this is the big G-man himself, George Washington. Although he has more hair than our greyscale friend, and as an important figure I do not think he would be stuck over by the window.
It occurs to me that whenever the signing of the Declaration of Independence comes up, it's this scene I picture, this exact room, even if I picture it with more "realistic" people. Yet another way The Simpsons has poisoned my brain.
This post is part of my "Every Simpsons Character Ever" series. For a list of my rules in this project, click here.