Try this,
First find an icon file (*.tga, *.pic, *.tiff, *.jpg, *.bmp, e.t.c.) that appears right your material you want to have.
Go to View > Model SetUp > Color and Appearance.
Click Add > Detail > Texture toolbar > click Map find your icon file you have founded, that you want your part or surface to be appearenced with.
Then return to the appearance window and SET the new color to the part or surfaces you want.
Shade the model and see the result.
regards
xcad