Brad,

    Not much to be done other than to observe. The researcher from link#4 may come up with something.

  http://extension.agron.iastate.edu/soybean/diseases_cercosporasojina.html

page 6 here:  http://soybean.uwex.edu/documents/DiagnosingLateSeasonSoybeanDiseases.pdf

"purple seed stain" page 2: http://www.australianoilseeds.com/__data/assets/file/0004/1201/Malcolm_Ryley-Effects_of_some_diseases_on_the_quality_of_culinary_soybean_seed.pdf

This guy may help us:  http://www.coker.edu/news/Flaherty_SCICU2009.html

Following from a Sep 2007 article: http://kentagextension.blogspot.com/2007_08_01_archive.html

Cercospora leaf spot and purple seed stain: Cercospora kikuchii can infect soybean seeds, pods, stems and leaves but is most commonly found on the seed. However, this year we are seeing some cases of leaf spot or leaf blight caused by this fungus. Infection is primarily occurring on the uppermost leaves and begins as reddish purple to reddish brown, angular to somewhat circular lesions on the soybean leaves. These lesions may coalesce to kill larger areas of leaf tissue. The uppermost trifoliolate leaf and petiole may be blighted and brown. The most striking symptom of this disease has been the premature yellowing and then blighting of the youngest, upper leaves over large areas of affected fields. In most fields, the symptoms have not progressed down the plants more than one or two nodes. Pods at the uppermost node may develop round, reddish purple to reddish brown lesions. This pathogen may also infect seed causing purple seed stain. Infected seeds show a conspicuous discoloration ranging in color from pink to pale purple to dark purple. The discoloration may range from small specks to large blotches which cover the entire surface of the seed coat. Temperatures of 82 to 86°F with extended periods of high humidity favor disease development.