If you're willing to accept that a JPEG is an arrangement of atoms in an SSD then why isn't the experience of the color red an arrangement of neural impulses in the brain?

No; the JPEG is a pattern.

There are a variety of ways we could recognize the pattern.

+ The series of bits you start with.

+ The bitmap on the screen.

+ the BMP which would also generate that bitmap.

+ The GIF which results in the same frame.

+ The emotional impression you take away from it. "That meme I remember so well"

And so on.

The JPEG is closer to qualia than is the arrangement of bits; closer to "your experience".

I don't agree with the person you are replying to at all. But I can still respect their point that there's a distinction to be made (or at least argued for) that the kinds of explanations we give for JPEGs are ultimately physicalist explanations. Everything on your list is a different physical medium a JPEG could be realized on (though maybe some would debate the last one).

But the person you are replying to probably wants to argue that qualitative experiences aren't realized on any physical sort of anything, let alone translatable across various physical mediums.

Now, again, I think that argument is wrong- I think these experiences happen in our brain, though it's currently unclear exactly how - but I at least understand their impulse to put those experiences in a different category than a JPEG, and why the ability to translate a JPEG across different mediums wouldn't speak to the concern they are raising.

Well, technically photons are massless and don't have "volume" in the common sense of that word. Red photons do have a particular energy, but I don't think any photons in the real world have exactly the amount of energy that a theoretical "red photon" is defined to have.

The JPEG is not a JPEG until it's processed by a program. Until then, it's just an arrangement of bits. Likewise, light has no color until it's absorbed by your retina and processed by your brain. Until then, it's just a photon of a certain wavelength.