Per USMC Uniform Regs Paragraph 4002.3.b
b. Anodized breast insignia will be worn on all evening dress and dress uniforms. Either anodized or oxidized breast insignia may be worn at the individual’s option on the service uniforms, but mixing of anodized and oxidized breast insignia is not authorized. When breast insignia is worn on the utility uniform, shiny or oxidized/antique breast insignia will be worn at the individual’s option (Pres MCUB decision 8 Oct 03), with the exception that subdued brown or black breast insignia may be prescribed in a field environment in lieu of oxidized breast insignia.