Not sure Andy. If they were painted in the US, presumably in 'equivalent colours', it may be that they were done as 'every second aircraft', or one side of the production line as a mirror image of the other, or some similar system. If done at the MU, I think in Egypt, then maybe the 'old' system was employed.
Whatever system was used, it's evident from many photos that the 'mirror image' schemes existed for some time on the P-40 in the Middle East.