My colleague is very upset that I did not clean the coffee machine

Just to give a clear answer to the being upset part:

From your description it's pretty obvious why he would be upset: You come over for coffee. You find that you'd need to actually do your share in maintaining the machine. Then you decide you don't want to bother and support the "common good" of having a working coffee machine. You even have the audacity to publicly proclaim that before you turn around. Yeah, I'd be pissed too of such a clear sign of anti-social behaviour regarding shared resources, easily assuming you'll try again in half an hour in the hope someone else cleaned the machine.

Now, you might clean the machine every night all night long, but your colleague might not know that. All he has is this episode that can easily paint you as an egoist and explains to him why he has to clean the machine "all the time" (in his perception) when he wants coffee.

As others already pointed out, the core issue might be that you need a clear policy of whose job it is to clean the machine to avoid such conflicts.

Here's what I think happened. I know this phenomenon from photocopiers. There are these people who use a photocopier and when it breaks down or runs out of paper in the middle of their job, instead of fixing it (if possible), alerting a technician, or getting new paper, they just leave and go to a different machine, leaving the next person to handle the trouble, the load of uselessly printed paper after the tray is replaced, etc.

This behaviour, with some justification, is considered parasitic.

Now, while you do clean the machine after yourself, the offended colleague may not have known. So, when you made your public statement about not getting coffee because the machine is not in current shape to provide and needs to be cleaned, it sounds as if you would engage in a weak type of "photocopier parasitism" ("the pleasure of getting coffee is less than the displeasure of having to clean it, I'll wait until somebody else does it") and even declare this openly so.

Now, you state clearly that you clean after yourself. Since this is so, you could state to that person: "Do note, I actually always clean the coffee machine after I use it [of course, that needs to be true]. So I believe that I deserve the occasional bit of freedom to be disinclined to clean it also in addition before I use it. I would therefore appreciate it if you ceased bringing this topic up in the future."

Apart from that, the cleaning list of Old_Lamplighter sounds like a constructive idea, except that I suspect it will be even less reliably used than the bathroom cleaning lists which no one really seems to ever check.

Note that this response is slightly contrarian and is appropriate if you decide that the other person is not entitled to an apology; don't use it if you prefer to clear the air by an apology.

Whether this is the case you would probably make dependent on your past interaction history with that person.

Your perspective isn't wrong. His perspective probably isn't wrong either. You think the last person to use the machine before it needs cleaning should be the one to clean it. He probably thinks it should be the next person. Neither of you are inherently right or wrong because in reality, maintaining the machine is the shared responsibility of all the coffee drinkers in the office. You were probably thinking "The machine should've been cleaned when I went to use it. Now I can't have coffee because someone didn't do their job." He's probably thinking, "this entitled jerk thinks cleaning the machine is beneath him."

I suggest you work with him and the other coffee drinkers to come up with a rule you can agree on. It doesn't matter too much what the rule is as long as everyone agrees. Rules are often arbitrary (like which side of the road you drive on) but it's still important that people follow them for obvious reasons.

There is a term "tragedy of the commons", and the coffee maker is pretty much the Ur example of it. If everybody is responsible for something, then nobody is.

Your cow orker is angry over the coffee maker not being maintained, and you just made a joke when he was already annoyed. As you've said, you cleaned it in the past, and it's not assigned to you to do. There's nothing you can do about his ire.

Your perspective is not wrong. If your company wants to address it, the coffee machine should have scheduled cleanings, with people assigned or volunteering to do it. (maybe a signup sheet?)

Don't overthink this. But if you want to address the problem yourself, you could put a sheet next to it with two columns ("cleaned by" and "date") and have whoever cleans it, sign. That way you have a record of who does, and who does not clean the machine. It doesn't have to be a policy, but it will at least make it clear that you're cleaning it from time to time.

I think your colleague is upset about your comment to everyone in the room, not failing to clean the machine. You could have left without a coffee or a comment. By making an announcement, perhaps in a tone that said "I am making a joke here" you implicitly criticized the sign. Or perhaps your comment might have sounded like "oh hahaha I love drinking your coffee but I never clean the machine, who would do that, I am too important to clean machines, I'm going to go get coffee somewhere else because I like other people to clean up after me." That isn't what you meant, but it may be what they heard.

Since your colleague won't stop bringing it up, you need to make things right in order to go back to a normal office atmosphere. Next time you see the colleague, say something like "I never expected to upset you by poking fun at myself about the coffee machine." This may lead to an immediate argument that you were in fact poking fun at the sign or the colleague himself, or that you were saying laziness is good, or any other number of things that this colleague has been brewing in his head for a while. If that happens, deliver a sincere apology:

Oh, wow. I am sorry. I've really upset you with that comment. It was thoughtless. I will be more careful making jokes in the future.

Do not say you are sorry IF the person was upset: you know darn well they are upset. Do not say you didn't intend to upset them; while useful information, it is not part of an apology. Acknowledge what you did clearly and name it. Then talk about how you will make it right. Don't make it right by cleaning the coffee machine: this is about how you spoke, not what you did or didn't clean.

If your "I never expected" line above just leads to a grunt, or a "well, you did" then your apology can't be quite as direct. You could say something like

I'm sorry. Since you keep mentioning it, I must have upset you with that thoughtless comment. I will be more careful making jokes in the future.

Don't press the colleague to agree they were upset, nor to accept your apology.

In either case, if the colleague brings it up again after you've genuinely and properly apologized, you can now say something like

Is this going to be a thing for the rest of my life?

or, if no-one else is around

Are you ever going to drop that? I have apologized. Is there something further you are expecting from me over my thoughtless joke 10 days ago?

Don't do that in front of people, it's a little confrontational, and embarrassment in front of others is what started all this.

Coffee machine etiquette is a weird thing. Some people take offense at petty infractions, they just have a different perspective. You're not going to convince him through reason that what he's doing is disproportionate to the offense.

The best thing you can do is wait for the next time the machine is dirty then go in there and clean it like it's never been cleaned before. Maybe stock some artisanal coffee and then ask the offended co-worker if he would like a cup of coffee, serve it to him and anyone else and apologize for not cleaning the machine when it was your "turn".

Also, keep in mind that by making a big deal about this, the coworker is hurting himself far more than he is hurting you. The others laughed when you quipped about not wanting coffee. They're probably wondering when the guy will drop his grudge as much as you are.

If you do nothing and don't care what this person thinks that's fine. But if you want to get along with this person, I believe some type of gesture like I described above is a good idea and people will see it as generous.

BTW... what kind of office has communal coffee, now, during the pandemic?