Avoiding “illegal” colors would be as simple as avoiding illegal firearms currently is.
I see where you’re going with this though. “Where is the line one cannot cross?”
A weapon is its parts, is my point.
How those parts are used determines what a weapon does and how.
The total of that weapons parts make it a functional arm.
If “arms” is undefined, anything that is part of a particular arm falls into that category, does it not?
But, is the rest not moot? Radioactive and biologically hazardous materials being used on people is already and act of war or terrorism. And the citizens are to have the final word per the constitution.
The line is what then affects others. At which point, those affected require the arms most suited to their purpose in defense. Not arms suited to an arbitrary or bureaucratic purpose.
It’s no different than having vehicles limited.
Only those who can demonstrate a need can own a V8 engine.
Fuel tanks should be limited to 5 gallons to prevent criminals from escaping the police.
Mufflers are only used by those up to no good so they should be registered.
I feel extraordinarily absurd using their arguments for limits like that, but it seems a decent comparison.
But we have all kinds of laws like that already. How about speed limits? Some people may be capable of driving responsibly at 120 mph and others aren’t. Since there is no practical way of determining who should be allowed to drive 120 mph and who shouldn’t be, we have speed limits that apply to every one. To some degree, that’s the nature of most of our laws. There’s nothing unconstitutional about it. The question of whether an individual instance goes too far is a judgement which needs to be made in each individual case. The Constitution is there to set limits to how restrictive laws can be, but within those limitations, laws by their very nature generally limit our freedoms to some extent.