Tim,
5-L is a very light grey, close to white. It would be impossible to tell in B&W photos. Have to remember that white was not a large stock color in the USN, 5-D and 5-L were premixed colors, and when they were discontinued for exterior camo uses in December of 1941 (Measure 1), they no doubt had a surplus.
Either way, 5-L or white, I seriously doubt anyone would be able to second guess you, because the two guys with opposite opinions will off arguing in the corner about it!
J