There are plenty of gun skins to unlock in Battlefield V. Each weapon has a bunch of different styles that can be applied to it, and you can get new skins by purchasing them with Company Coins, or you can go about the things the hard way and unlock them by completing challenges.
As you look at your weapon in the customizations screen you’ll notice that there are a bunch of common, uncommon, and rare skins that are not available by default. The fastest way to get some of these rare skins is to just pay the amount of company coins to get them.
However, there are a couple that are not for sale. These Epic and Rare skins need to be unlocked by completing Mastery and Proficiency challenges with that weapon. As you level your gun in Battlefield V you will unlock different things.
During the first four levels you will unlock common skins for the weapon. Once you reach level 5 with a weapon you will get a Proficiency Challenge. At level 6 up to level 10 you earn uncommon skins and when you complete the gun leveling at level 10 you will get a Mastery Challenge unlocked.
To get the rare and epic skins (like the gold gun skins) you’ll need to complete these challenges. The Mastery Challenge and Proficiency Challenge can be added through the Assignments tab on the main menu. Once you make these challenges active they will throw you increasingly difficult tasks to complete in game with the weapon. For each one you complete you will earn a Rare or Epic piece of a gun skin. Once you’ve made your way through the challenges you will have a full set for your weapon.