Uniform/Gear question

Can anyone explain how uniforms work? I see the standard uniform and I see the OD green uniform…green’d out patches. Are you allowed to use both?

Also are optics and lights allowed to be used on pistols/patrol rifles? I see the old woven leather holster/belt and wonder why not use more updated gear.

Wouldn’t you want the most modern gear to give the greatest tactical advantage when working alone in the wild? Anyone have any insight?