Here's a couple more links to pictures.
I'm assuming that the first link represents"dark slate gray/light graystone"
I'm assuming that the second link represents "dark/light slate gray

First link:

http://www.autocult.com.au/img/galle...oitAuto296.jpg



Second link:

http://image.automotive.com/f/auto-s...erior-dash.jpg

Or maybe these two pics are identical but the lighting makes it appear different?

 

You are correct
The first link represents"dark slate gray/light graystone"
The second link represents "dark/light slate gray"

Although the second link looks a little darker than the actual colors and is more accurately reflected on the Dodge web site's default Avenger interior pictures.

dark/light slate gray:
http://www.dodge.com/shared/2008/ave..._phtgal_04.jpg