Somewhere in between is about right. The pic on the left shows a fairly close representation on the control column, whilst that on the left, allowing for the shadow and slight under exposure, shows more towards the overall appearance. I've checked some transparencies of the P40 which used to be at Duxford in the mid 1980s, and it looks like a sort of Olive Green with a hint of blue, giving that brighter tone seen on the control column. All of this had a slight sheen, not quite semi gloss, but slightly less than semi matt, if that makes sense?!
The seat, BTW, was matt Olive Drab, as seen in the pic on the right.