So, after watching the video a bunch of times, trying with the Pantone colors, etc., I ended up using my iPad to take screen shots of the paint pot lids and then using the Behr (Home Depot’s main brand like Dulux) app to select areas of the image multiple times until I got a palette that looks close for all the main colors. I bought a pot of Citadel Steel Legion Drab and yes it is too dark to be the undercoat color; what he is using as a base layer for the buildings is basically a khaki color with maybe a slight greenish-Gray tinge. But If you plan to do the walnut stain all over treatment, it will blend everything nicely.
Two things to keep in mind: I have read and talked to several owners of the factory painted models and seen unboxing videos, and the factory results range from slightly inconsistent to wildly divergent in terms of quality and keeping to the paint scheme in the how-to-paint video. Also, very slight variations are not perceptible by the human eye, especially since a lot will depend on the results of the final stain. Finally, he did mention a light dry brush pass *after* the all over stain coat, such as on the rocks and thatch. So I think this is a case of “close enough is good enough” and the minor variations are part of the organic charm. I also think it might be good to choose a water based walnut stain if you are going to do that step. Easier cleanup and quicker drying.
The one thing I think these models need is lots of moss in the cracks and crannies, depicted as light to dark green flocking stuck on with PVA-water mix dribbles. That bit of color contrast will really help, especially if you do it in the shadowed areas and in between the stone wall pavers especially where the greenish brown stones are. I’ve given up matching Pantone colors.