united-states
This question does not indicate in what jurisdiction the hypothetical events take place. Since they are hypothetical, I am going to assume the United States. Perhaps other answers will be given for other jurisdictions. I would be interested to read such answers.
The Officer's Authority
In the hypothetical situation described, it would appear that the police officer had no warrant or other court order, and that he did not have any probable cause to believe that any criminal activity was in progress, or that any crime had been committed. Indeed it would appear that the officer did not even have the "reasonable suspicion" required for a so-called Terry stop (named for the case, Terry v. Ohio, 392 U.S. 1 (1968) in which such stops were declared legal). In any case the encounter described is not a Terry stop, because such a stop takes place "on the street" or in a public place, not on private property.
So far it seems that the police office is acting without lawful authority. When the man orders the officer to leave his property, the demand is lawful, and by not leaving, the officer becomes a trespasser, unless the officer has some justification not mentioned in the question.
The Duty to Comply
However, once the officer starts to give orders, the other person must generally treat them as lawful. There are exceptions: Officers cannot compel people to commit crimes, nor to submit to rape or murder. But orders given for the ostensible protection of the officer have particular deference. As the US Supreme court said in Terry v. Ohio (cited above):
... we cannot blind ourselves to the need for law enforcement officers to protect themselves and other prospective victims of violence in situations where they may lack probable cause for an arrest. When an officer is justified in believing that the individual whose suspicious behavior he is investigating at close range is armed and presently dangerous to the officer or to others, it would appear to be clearly unreasonable to deny the officer the power to take necessary measures to determine whether the person is, in fact, carrying a weapon and to neutralize the threat of physical harm. (emphasis added)
Resisting the Officer
Following the logic of Terry Courts tend to give deference to police assertions of the need to protect themselves. The modern tread is to require citizens to submit to police orders in such cases, even if the citizen believes the order to be unlawful, and even if the court eventually agrees. In many states, violent resistance to such orders would be a crime even if the order was later ruled unlawful.
In every US state, he use of deadly force, by drawing and firing a gun at a police officer who has issued possibly unlawful orders, but has not threatened the life or well being of anyone, and has not used any force at all, would be clearly criminal.
Nolo Press's article on "Resisting Unlawful arrest" says:
Historically, American citizens were legally entitled to use reasonable force to resist unlawful arrest. Some states continue to follow this rule, while others don’t.
A statute rejecting the traditional rule might say something like this: “You can’t use force to resist if you know or should know that you’re being arrested by a police officer, regardless of whether the arrest is legal.”
...
It’s critical to note that one can be convicted of resisting arrest even without having committed the crime that was the basis for the arrest.
It should be understood that even in those US states which follow the "traditional rule" and permit resistance to an unlawful arrest, only "reasonable force" is permitted. Shooting a gun at an officer is deadly force, and will not be reasonable unless the person has a justified belief that the officer is about to kill or seriously injure the arrestee or another person without justification.
Also, if the arrest is somehow lawful, even though the arrestee reasonably believed it to be unlawful, the use of even "reasonable" force is no longer permitted, and the arrestee may be convicted of resisting arrestee and other crimes. This makes resistance a dangerous gamble, even in states that follow the traditional rule.
In addition, resistance is all too likely to lead to escalation of the conflict, and end with the arrestee shot dead or seriously injured. Even if the officer's actions are later held unlawful, that will not bring the arrestee back to life.
Under Color of Law
The question asks if the office's actions are taken "under color of law". They are, in US law. This does not mean that the acts are lawful or proper. Rather it means that they are take by means of legal authority. Such acts therefore constitute "state action" subject to the limitations of the 14th Amendment to the US Federal Constitution. The Wikipedia article on this topic (linked above) says:
... just because something is done with the "color of law" does not mean that the action was lawful. When police act outside their lawful authority and violate the civil rights of a citizen, the FBI is tasked with investigating.
The well known "section 1983" (42 USC. § 1983) provides a private right of action in such cases, saying:
Every person who under color of any statute, ordinance, regulation, custom, or usage, of any State or Territory or the District of Columbia, subjects, or causes to be subjected, any citizen of the United States or other person within the jurisdiction thereof to the deprivation of any rights, privileges, or immunities secured by the Constitution and laws, shall be liable to the party injured in an action at law, Suit in equity, or other proper proceeding for redress ...
Here the hypothetical officer's entry onto private property, his refusal to leave when ordered by the owner, his order to put down the pistol and step away from the other guns (implying an arrest or detention), his order to stop recording and turn over the record, and his drawing of his firearm are all acts taken "under color of law", and had the citizen submitted, he could have subsequently filed a Sec 1983 suit against the officer, although he would have had to establish harm done to collect more than nominal damages. The officer is relying on his authority as a police officer to enforce his orders, and indeed to support his presence on private property. This makes his actions clearly done "under color of law".
