Previous Message

Beginning right after Pearl Harbor, ships being ordered to paint into Ms.11 were ordered to do so, but to substitute 5-N for 5-S. Until the June 1942 revision to SHIPS-2 officially promulgated Ms.21, the measure continued to be known as 11. Also, from Alan Raven's camo series in PSM in the '90s:

"Since early 194l the Pacific Fleet had been looking for the ideal concealment colors, especially against aircraft. The Dark Gray 5-D proved effective, but was not blue enough, and to this end two destroyers were tested with a very dark pure ultramarine blue (Sapphire Blue). As a color it was effective, but had poor durability. A new color tested in the Pacific in December 1941 on the destroyer FLUSSER proved successful, and it was decided to have the entire fleet so painted. However, there were no stocks available for 5-N Navy Blue (as it was called) for Pacific Fleet use until several weeks into 1942. Change over to overall 5-N (known as Measure 21) took some time to accomplish, and it was not until early 1943 that the whole fleet sported the new measure."

So, there's another non-answer you can stir into the pot.