Ok so finally here's the breakdown. If you need more information on it feel free to ask. I of course use here and there some Level, Brightness/Contrast and Hue/Saturation to achieve the final look of the texture but you have the overall process shown on the breakdown. I also sometimes create a copy of the second color…
Thanks you guys. As you seems to like it I'll continue the whole thing with this art style. More to come during the next week. Can't work over it during this week-end.