Firearms, shooting sports...
Firearms by en large have been a part of the US culture & heritage since the very start. Since then, many people have customized their weapons or modified them to reflect the owner's or user's taste/style.
Like it or not, guns have become a huge fad to many in this country and they want to use bright colors, engraving, custom grips, artwork, etc.
I, for one, would think it'd be extremely difficult to explain to a homicide investigator or a jury in open court why you had some
Zombie Killer brand ammunition or had a Grim Reaper on handgun grips then had a use-of-force incident.
Humor, sarcasism and/or fads do not really have a place in real armed protection or defense.
Now, for general target practice, collecting or for having a "BBQ gun", then you can have a firearm with these features.
I know a well known film industry stunt performer & Korea war era combat veteran who's wife totes a K frame .357magnum with pink Hogue grips,
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I've also seen increased use of bright pink handcuffs by female law enforcement officers & bail enforcement agents.
CF