I tried to create a custom pap weapon and everything worked except for the purple glow when you shoot. Does anyone know how to add this?

I'm guessing you want to change its muzzleflash fx to make it feel like other pap'd guns. You need to find the muzzleflash fx part in your weapon file and replace with a fitting muzzleflash fx. Just check a stock weapon's normal and pap'd versions' weapon files and you'll be able to tell the difference.