Pain is the heat.
Now refine it further. Pain is the radiation detected by the skin.
Wow. That is at odds with any scientific or philosophical model I believe I have ever come across.

Joy. You’re continuing to appeal to authority in spite of being explicitly told not to.
So, to that appeal, perhaps if you hadn’t selectively cherry-picked the middle step in a series intended to demonstrate how using imprecise LANGUAGE keeps tripping you up might help you (ironically) put things into proper perspective? And then you addressing the coder/code/decoder breakdown certainly would help.
You keep avoiding the fact that a brain can do whatever it does AND a message can contain information independently of whatever the brain is doing. Those are not mutually exclusive concepts.
There can exist a coder, a code and a decoder. And yes, since the decoder is decoding the coded message, that necessarily means that they are RECREATING the message on their end. They are unpacking the package. So if you were to JUST LOOK AT THE DECODER, it would seem as if the message is only happening at their end.
But is that objectively the case? No, it is not. There is also the coder and the code that objectively exists too. But there is no way to prove that, only infer it.
And guess what? Just like someone decoding a coded message can get the message
wrong, so can a brain.
But it would help matters considerably if you would stop thinking in binary terms.
In the study you referenced above regarding blue and red effecting pain levels, there is a key word: associated.
"These results uphold the first hypothesis that when the noxious stimulus is associated with a red visual cue, signalling that the stimulus is hot, it hurts more and is perceived as hotter than when the same stimulus is associated with a blue visual cue, signalling that the stimulus is cold."
Taking us all the way back around to the beginning of this merry-go-round. Some people (some “brains”) ASSOCIATE the color red with “hot” and the color blue with “cold.”
What does that mean? Break down the actual process, not the vapid sound bite. Here’s yet another clue: you can’t remove the word “associated” and achieve the same result, so what is it that already happened prior to the person who sounds the pain alarm when they see the color red? What is it that the brain is
associating?
I’ll answer it for you. At some point in time previously, that person burned themselves on something that was actually (i.e., objectively) “hot” and emanating the wavelength we call “red.” Thus, whenever that person sees the same wavelength, that
association gets triggered and that is what in turn triggers a damage alert response.
Iow, the brain can be tricked into sounding the alarm we call “pain.” Why? Because, surprise, surprise, brains are not infallible, omniscient machines, but the very fact that there is a mechanism that associates argues, once again (just like the rods and cones) that the process comes from an objective condition.
Iow, you’re providing exceptions that prove the rule.
So here’s what you’re going to have to wrap your head around. Yes, everything happens in our brains. That is a brute fact. Does it ALSO happen in a like manner outside our brains? We can’t ever know that definitively, we can only infer that. Those two conditions, however, are not mutually exclusive.
Which brings us—as always—back to WHY (and HOW) we developed rods and cones (i.e., the ability to color code) in the first place? The most logical answer to that question is because color—light wavelengths—are, as you have already agreed, objective properties of light.
Just as Morse code conveys a specific, objective message and just as the guy sitting on the other end of the telegraph wire must translate (aka, decode) the series of clicks and pauses and just like the message that guy is decoding
technically only gets decoded inside his brain, so too does the thing itself send us coded information about the thing itself.
But at the exact same time, the decoder
already knows what the code is, so it’s entirely possible that it might mistakenly hear a similar series of clicks and pauses that was NOT sent deliberately and because his job is to decode coded messages, he gets it wrong. That last series of clicks and pauses did NOT come from the telegraph machine—as he believed—but from something else.
OR, he could be listening to a message and writing down the code on his little pad of paper and hear a series of clicks and pauses that were identical to ANOTHER previous message he took that turned out to be a message that his wife had died and so, on this day five years after that tragic message he decoded, his brain hears the same clicks and pauses as before and it triggers an
associated memory that causes him to become emotionally and physically traumatized all over again and guess what? He mistakenly decodes the wrong the message and instead of delivering the message, “Your wife has been killed” he delivers the message, “Your wife is going to be just fine” or the like, because something his brain
associated with those particular clicks and pauses caused him to deviate from the objective condition into a subjective condition.
Layers upon layers upon layers, only with the complexity we’re talking about, those layers are more like holograms in a massive, dynamic, Venn diagram of feedback loops and interactions and updates and overwrites that constantly happen at speeds so fast we—the animated selves—have no concept of and are not even aware are occurring.