A thought experiment: Assume all guns were pink by law tomorrow.
Would that have an impact on the number of gun-related deaths? What percentage?
Would it have an impact on the number of mass shootings?
This is not an actual policy suggestion, so the feasibility of such a policy is irrelevant. It is more a question of the psychological impact of the color on the behavior of gun users (otherwise the usage of the color pink stays the same). Choose other colors if that's relevant for your answer.
Disclaimer: This is not my idea and you can quickly find out who asked it on twitter, but there are no answers on twitter yet, so better google somewhere else (also to avoid politics the mind-killer). I will reveal the source of the question later in the comments.