In the US Navy in the 60's most life preservers and vests were orange and some times white any gray ones had been painted over by the deck crew. (The complete Boatswain's mate manual: "if it movies salute it, if it doesn't paint it"). The white ones were often decorations on the quarter deck . These had the name of the ship and its hull classification/number.
A comment on color schemes and painting of models. Models are a work of art and represents how the builder sees the model. with that in mind I would paint the model to match the John W Brown. most people would compare the model to the John W Brown.
A feather comment on gray life preservers the ocean very often has a a blackish color especially in stormy weather. a gray life preserver would not stand out in that kind of sea.