Glen, according to the Rock Island Technical Society, only units 940, 945 and 947 received the blue "ROCK" scheme. You can check their website at:
http://www.simpson.edu/~RITS/
The specific link for the SW1500 write up is...
http://www.simpson.edu/~RITS/equipment/ ... w1500.html
Finally, is this what you are referring to?
http://www.simpson.edu/~RITS/equipment/sw1500/947.jpeg
Art Audley, AA3RT
Moderator: Railroad Radio & Communications, Railroads in Books, Magazines, Music, TV and other Media, General Discussion: Fallen Trolley & Interurban Lines, General Discussion: Shortline, Industrial & Military Railroads,