The oooold Frisco was "backwards" with black crossbucks with those old reflective dots spelling out the letters. ATSF were white saying "Railroad Crossing" then down the post vertically "Look out for the cars". I, ummm, "liberated" one that was taken down and lying on the ground, but the lettering was too bad to be legible. Old white lead paint would turn yellowish in the presence of some chemicals, but in OK, AR and MO as a child, I never saw a yellow crossbuck.