I think the eye is an imperfect computer and subject to a number of variables. I had a humbling experience. When Zero amber/grey seeking I stumbled on a photo of a rebuilt Zero that reportedly has a very good rendition of the real deal:
I put that into Corel paint and ran my cursor over it and watched the RGB values - they varied greatly by moving the mouse a very small bit, so the eye is kind of averaging. I know some fine modelers that are content with ballpark colors and use washes and weathering to bring things into line.
The guy that really knows I think everything about the Zero color (and IJ aircraft colors in general) is author Nick Millman who also runs the site Aviation of Japan
http://www.aviationofjapan.com/ . He did a long and very detailed PDF on the subject for $10 and it was well worth it. His samples are mostly quantified in Munsell rather than FS. He argues that a Zero in good condition is Munsell 7.4 Y 5.8/2.0. He thinks Tamiya XF76 is okay for a faded Zero, but too gray for the original. He finds MA Hemp to be too dark. The closest commercial paint he believes is LifeColor RLM 02 (UAO71) which vendors peg at FS3651 - very close to Vallejo 886. But Nick thinks the LC should be lighter. I stumbled on a formula of Feldgrau 830, khaki gray 880, green gray 971 as a good mix. Who knows. Odd color: amber gray - so figure, gray, khaki and green, with the bulk of the green being "fugitive." Nick gave me samples for an early war Val which carried a color that was more amber, and if a photo got the light wrong the plane looked light green - despite the fact there was almost no green in the mix.
BTW: I built a "Secial Attack" A6M2 a while back and Millman said that the Nakajima IJN Green was very dark - "almost black." I spent some time on that one and think he's right.
Do keep us up to date on any more of your labor - very helpful to people like me who really like water based acrylics.
Eric