First, olive drab will only provide the P-38 with limited concealment when it is seen against green earth. Against the sky, water, or earth of a color besides green (desert, bare dirt, snow, etc.) it will not be of any advantage.
Second, the P-38J-25-Lo, the most significant P-38J in numbers produced, was essentially the same as the P-38L series. The P-38L did have a better engine, but it was restricted by the USAAF to the same level as that of the P-38J-25-Lo, so there is nor real difference.
Third, do not expect the P-38 to get anything soon. It does not even have the new 3D model nor the new damage model. And we've been told that current planes will likely remain the same until they have a serious number of new planes and vehicles in the game finished.
You'll find the P-38 to be low on the list for anyone but a serious P-38 enthusiast, few of which ever make it into the business end of flight sims.
And the current 3D model of the P-38 prevents any really significant changes in the skin, so there have been very few if any user skins, and I haven't seen any listed as being accepted by HTC.