Depends on which county you live in. Answered by Mr. Lee Thorne, District Five Engineer/Manager WV DOH:
JEFFERSON COUNTY: The Jefferson County 911 director, pursued through the former Traffic Engineering Director an exception and there are no route numbers on street signs in Jefferson County. As you stated, generally a green sign with white letters indicates a named road in the WV State Highway System and brown signs are for private roads. However, we are aware that there are a few cases where the wrong color sign has been installed and we are working to have them corrected. As part of this exception, Jefferson County government maintains all of the street signs in that county.
BERKELEY, GRANT, HAMPSHIRE, HARDY, MINERAL and MORGAN COUNTIES: As far as I know, there is no rule that dictates the color of the signs for private roads in the remaining counties in District Five. Some are green and some are blue. However, if there is no route number then they would be considered a private road and the WVDOH would not perform maintenance on them. (Pendleton County is located in District 8)