Johnston was painted in Measure 21, which calls for overall 5-N Navy Blue. She's wearing this in the work-up photo I've attached.
Destroyers wore three types of patterns by 1943-1944, Ms 21, Ms 22, and dazzle, Ms 31, 32, or 33.
'Gray' seems to be the most prevelant response from the WW2 vets, even with color photographic evidence to the contrary...remember, most of those guys are now in their 80s...
5-N did have a tendency to fade, a perfect example is the USS NJ, she was known as the 'Black Dragon' because her blue paint had faded to a dark gray. Later on in the war, the USN did revert to neutral shades of gray, but Johnston had been sunk long before these tech orders came down.
The nature of the paints was simple...you had tinting material 5-TM, and base 5-B. 5-B was white, and 5-TM was a very dark purple/blue. By mixing pre-determined amounts of the 5-TM with 5-B, you got all of the shades used by the USN, 5-H, 5-O, and 5-N.
Jeff