Do you think skins really affect the gameplay?

Usually,on games such as League and Overwatch, such a thing exists because of the different textures and colours in particles.

Now for gun colours,unless there is a stealth factor involved(like Call Of Duty),I don't think it applies to a better gaming experience.
It's most likely something you are used to and like,so you focus on killing and not admiring some cool patterns on a piece of metal.