Hi, and welcome to the site. Interesting schemes there, I assume they are squad skins? The metallic sheen is caused by the in game lighting effects in IL2/PF. I never fully understood how it worked but from experience I found that darker colours with lots of detail seemed to reflect less light. For example, an olive drab P47 with lots of dirt on it has quite a matted appearence, where as a pale grey plane with only panel lines seem more reflective for some reason.
I seem to remember that you can adjust the lighting in IL2/PF so that maybe another option. I'm more MSFS minded these days but maybe one of our IL2 experts can shed some light on it? (if you excuse the pun!)