I notice a lot of Tamiya products in your photos so here's my preferred Tamiya PC.10 Mix:
Equal amounts of XF-62 Olive Drab, XF-51 Khaki Drab, and XF-55 Desert Tan.
To that add about half of one of those measures of XF-10 Flat Brown. The brown can be decreased or increased depending on the "brownish tint" you desire, and really increased to provide the more "chocolaty brown" PC-12 color.
If you prefer enamels I also use a 50/50 mix of Model Master Olive Drab SKU 17110 and Faded Olive Drab SKU 20510. You can add some dark brown or even red to that to experiment.
Keep in mind we'll never know the one true version of PC.10, it's a matter of personal interpretation, taste, and degree of sanity!

Have fun!
Cheers,
Lance