I found this after searching like crazy. Its a color manual from Sherwin Williams auto paint. You can find the color codes for the different parts of your Mustang including wheels and interior by looking at the body paint code on pages 113 to 115. I wanted the color code for the center console/audio climate panel. They have a color manual for cars up to 2012. I have a 2013 but I know all the colors for my interior are the same as 2012.
http://www.sherwin-automotive.com/collision-repair/color-tools-information/color-reference/color-manuals/
http://www.sherwin-automotive.com/collision-repair/color-tools-information/color-reference/color-manuals/
