Look in "Config_Master.hpp"
->
cop_extendedSkins = false; //Enable or disable cop skins by level. Before enabling, you must add all the EIGHT files to textures folder. (It must be named as: cop_uniform.jpg + cop_uniform_1.jpg, cop_uniform_2.jpg...cop_uniform_6.jpg, cop_uniform_7.jpg; meaning cop_uniform = life_coplevel=0, cop_uniform_1 = life_coplevel=1, cop_uniform_2 = life_coplevel=2, etc...)