NCF – Extended list of Neutral creatures.

Regarding the initial and elemental magic, it's described in the creation legend: "Ascha separated and defined six 'colors' of magic floating in the cosmic void: Darkness, Light, Earth, Fire, Water, and Air." Thus, Ascha SEPARATED the magic from a single source (which, logically, is the initial magic). This again refers to the fact that Ascha is a dragon of Order, and she organized the chaotic super-magic into constituent aspects. And yet another reference that a world without any magic or religion is impossible, and that's why the Voidwalkers wanted to kill the god – then the entire system would collapse.
In the same creation legend, it is said that Urgash hates all of Ascha's creations and wants to plunge the world into primordial chaos.

Based on this logic, Ifrits should shimmer with all the colors of the rainbow and cast initial magic... I've gone too far... I need to think more.

Added 3 minutes ago
Regarding demonic magic, I completely agree.

Hmm... different sources write differently – perhaps due to the problem of forming and editing the lore throughout the fifth to seventh parts by the developers themselves – what you wrote, I found on the Asahn Might and Magic wiki.
What we have is that initial magic is woven from six elements.

Ascha separated and defined six 'colors' of magic floating in the cosmic void: Darkness, Light, Earth, Fire, Water, and Air. It was from these threads that she decided to weave the universe.

That is, Ascha separated them from all this mess, and Urgash transformed the initial magic (and therefore the six elements contained within it) creating what is called Chaos magic.
Based on this logic, Djinns should not cast spells randomly, but specifically, because they are spirits of ordered initial magic and can isolate the elements and apply them at their discretion, and Ifrits, in turn, use initial magic in the form of mixed and undifferentiated elements, and even transformed by Urgash, that is, the randomness of the spells cast is more suitable for Ifrits.
Another point about the fact that Ifrits should shimmer with all the colors of the rainbow and cast initial magic – but no!!! Demons are also primarily connected not with fire, but with initial magic, since they were created by Urgash, and not by Arcat, and their connection with fire is due only to Ascha's choice of the location of the prison for Urgash – she imprisoned him in the core of the planet, and it's hot there, hence the result.

Added 20 minutes ago
In general, I read the wiki again – it says that their appearance is not known for certain, but one of the theories is that the absorption of a Djinn's essence by some mage leads to such consequences – I need to remember that Djinns owe their origin to Sar-Ilam – maybe there is some connection here – who knows.
I think we need to base it on the lore, and add things (but so that it does not contradict the lore) since the alternative lore is not provided by the developers.
The question remains: How can we show the "Chaos Shield" ability in Heroes 5? So far, as I understand it, the fire shield has become the Chaos Shield – it's not quite the same, but given the Ifrit's connection with fire – why not. That is, the alternative upgrade can get the Wheel of Fortune, and the regular upgrade can get a random debuff.
And all three retain immunity to fire and the fire shield.