I have seen pubescence, especially in nature plants, in brown color against gray color. The two types are equally frequent among commercial varieties. In brown pubescent genotypes the hairs in the young plants are colorless, but after a few weeks' growth, many of the hairs grow on the stems and pods and to a lesser extent on the leaves with brown pigments.
Al-Ali, Adel Rashad
"Research Notes : General ideas about soybean genetics,"
Soybean Genetics Newsletter: Vol. 7
, Article 31.
Available at: http://lib.dr.iastate.edu/soybeangenetics/vol7/iss1/31