As you probably know, many USN aircraft were painted glossy blue in the 50s.
One source I have says the “midnight blue” was adopted in 1944 and remained the standard colour until 1955.
The A3D prototypes and early production aircraft..perhaps all 50 A3D-1s…were painted blue.
In one of my books, there is a photo of an A3D of VAH-1 on its first cruise in 1956 painted blue.
Since the A3D-1Qs were modifed from the first production batch, perhaps the answer is as simple as the Navy left them their original colour for a period before being repainted gray along with the rest of the A3D fleet.

Also, it it was doing “spy” work, perhaps the gloss Navy blue was judged to be a good camoflage colour for night use…and it would certainly blend in with other Navy aircraft of the period.