95% of the Benton County Home Guards Volunteer Regiment (aka German Regiment) were German immigrants and descendants from Cole Camp area. I have reconstructed the unit roster from National and State Archives records, and no Anderson's are included. However, there was a John W. Anderson in the nearby Johnson County H.G. unit, who was captured Near Knob Noster and later returned to his unit:

http://www.sos.mo.gov/TIF2PDFConsumer/DispPDF.aspx?fTiff=/archives/AdjutantGeneral/Civil_War/ServiceCards/s881/1240.tif&Fln=S356085.pdf

But there were also two John Anderson's in Benton County 1860, both 28, one from Ohio and one from Pennsylvania, and coming from northern states, they may have served with a Union unit. Can you provide more details? Is he buried in Benton County?

http://www.phelbs.com/hrftx/BCHG.htm