Actually, if you're looking for a match for Gunze's Middle Stone for a German Armour project, I'll guess that you're building a Dragon kit, becaues for some unknown reason, "Middle Stone" is the base colour they suggest for all their German kits with a "Dark Yellow" base.
Middle Stone is actually an RAF camouflage colour and to my eye, looks like it needs toning down for this purpose, so don't be too hung up on getting an exact match for what is essentially an incorrect colour.
Personally, I use Tamiya Dark Yellow toned down with Deck Tan, so I can't help with any suggestions for a Vallejo equivalent.
(Finding an exact match for Dark Yellow/Dunkelgelb - this is about as long a story as finding an exact match for Olive Drab, which you can see a few threads away)
Also, are you looking at the actual paints or are you looking at Vallejo's colour chart? I find that many of the examples on Vallejo's colour chart aren't anywhere near close to the actual paint in the jar.