Uh…hu.  

@ThePonyTheorist
 
Theories are fine, but it’s still head canon. The simplest explanation is that their magic is… magic. It doesn’t have a physical or biological explanation. That’s one of the defining characteristics of magic.

@Vinyl Fluff  
Magic centered in the eyes, or at least being involved in the main step (as well as being a gas): https://derpibooru.org/1411095?q=uploader_{3Atheponytheorist
 
The horn being a rune network: (More tenuous, but makes sense given then above) https://derpibooru.org/1447644?q=uploader}3Atheponytheorist
 
Additional rune-analysis to compare: https://derpibooru.org/1413234?q=uploader%3Atheponytheorist
 
Twi freaked at the loss of the horn, meaning that it’s an important step - but not necessarily the source of ‘magic’

@ThePonyTheorist  

 
That’s a whole lot of head canon. Why would magic center in the eyes? And why would Spike being a baby dragon mean he was wrong? Twilight didn’t correct him, and freaked out about the loss of her horn, indicating he was correct. Historically, the horn is the center of a unicorn’s magic.
 
In classical literature, the horn and the horn alone is the source of magic. That’s why removing it or damaging it stopped the unicorn from being able to use magic. The horn itself even had a name, the alicorn. Faust reused the name to refer to the race the two princesses were, but officially they were known as “pegasus unicorns” in show-related material. It wasn’t until the fans picked up Faust’s use and kept referring to them as Alicorns did it eventually make its way into the show, first being used in Magic Duel. There’s A LOT of mythology surrounding unicorns and their horns. Why reinvent the wheel?
 
I’m also wondering why people think their magic is a gas. Just because it looks “vapory” doesn’t mean it’s a gas. It doesn’t need a physical explanation about what it’s made of, it’s magic. The glow is simply a magical aura. In D&D the aura is called a dweomer.
 
The fact that characters don’t respond to the different colors like with QC/Cadance I believe is just a necessary plot contrivance. Otherwise the second a pony popped up with a different color they’d know something was wrong. A Canterlot Wedding would’ve been over real quick had Twilight pointed out “Cadance” was now using green magic, and Celestia (being her aunt) went “Oh yeah, what’s up with that, Cady?”

@Background Human  
And it seems totally different in nature to Equestrian magic, which appears to be a gas…  
Our theorycrafting has now hit critical mass, where we can see that the magic in EQG-land is different to that in Equestria. How fascinating.

That, or they changed it so the gag where Sunset didn’t realise she could levitate the book with unicorn magic would land. They have very similar magic colours (if going by EQG1).
 
Also, I’d like to add that the colour of the magic is never brought up in-universe:
 

 

 
Thus until we can have Ishi on about it, I’d argue that the magic colours is more for the sake of the audience (like aliens speaking english in sci-fi shows and movies) than something that is worthy of note in-universe.

From what I recall in Rainbow Rocks and Friendship Games, Humanland magic does seem to have properties consistent with EM radiation. The Dazzlings’ noxious amnesia gas might have been a type of cold plasma charged with magical energy.
 
EDIT: This, by the way, would explain why Equestrian magic is compatible with human electronics. They operate on similar scientific principles in-universe.

@Background Pony #E85B  
It’s more raw magic being blocked that i’m after. A beam would be the only thing that would work for that, but I don’t think we’ve seen that happen yet.
 
(Plus, that “shield” was a bit too wavy to be a shield. Maybe it wasn’t one, and they absorbed the fireball or something?)

@ThePonyTheorist  
No, she hasn’t yet.
 
I also forgot Twilight had a barrier when Sunset turned into a succubus and shot fireballs at her. That’s more what you were thinking about, right?

@Background Pony #E85B  
Has Rarity’s magic ever blocked MAGIC before, though?

“Has a shield ever been seen in the EQG movies?”
 
That’s what Rarity’s magic does.

@Background Pony #E85B
 
@Background Pony #E85B  

 
much more powerful then the geodes.
 
Good god my grammar is atrocious.

@PonyPon  
Trixie’s and Rarity’s were, but they were much powerful while the geodes. Gloriosa was already wearing five and she was mostly okay.

@Background Pony #7245  
Weren’t those both evil and mind-altering?

People: It’s more likely the animators screwed up.
 
That may be true, but it’s also fun to imagine in-verse headcanons that explain the screwups.

@Vinyl Fluff  
@ShimmeringGloriously  
Or, you know, the animators decided making Sunset’s magic color more distinguishable from Starlight’s was more important than satisfying some random bronies.

@OneOverTwo  
In that case, it could indicate a shift to friendship-based magic? Or just stronger magic.

@ThePonyTheorist  
Twilight’s aura was a different color in the first season before they changed it.

This did kind of happen twice before in equestria. The alicorn amulet turned Trixie’s magic red while Rarity’s turn green with that book Spike gave her.

@OneOverTwo  
That was only in the first episode, where they were trying to figure out what magic looked like to begin with (or, in an alternate view, what magic looks like to pony eyes - thus people not noticing Cadance’s green-glowing horn when she was Chrysalis)

It could just be a case of them just deciding her magic is colored different now.
 
They did that with Twilight real early on.

@ShimmeringGloriously  
Assume conscious intent at all times is my philosophy ;)
 
That, or simplification / low resolution (my argument for the equestrian writing being squiggles)

@Alexander Cupo  
Of course it did, that’s where all the magic comes from.

I believe the magic in the geodes came from Equestria in the first place.