Plasma and Energy Sword Colors

I’m bored so I thought I’d attempt an explanation of plasma colors in Halo canon.

Plasma bolts (projectiles)
One of the most common covenant weapons is the Plasma Rifle, which fires blue bolts of plasma. But why blue? -And why do the other weapons have different colors?
For the uninitiated, you should know that Plasma is the fourth state of matter, (after solids, liquids and gasses). Plasma exists naturally in all stars such as our sun, and can be created by simple human technology, such as arc-welding equipment.

Bungie showed great attention to detail by putting an electrical arc at the muzzle of each plasma weapon. It could canonically function similarly to the pilot flame on a human flamethrower, i.e. a catalyst to excite atoms in the plasma weapon.

It has been theorized that the plasma weapons create electromagnetic fields to contain and propel the plasma, And although this might make sense theoretically, I won’t go into the details of that. The inner workings and mechanics of the weapons can stay a mystery for now.

Our experience as humans gives us some intuition about the colors of light, but we need to make some distinctions to avoid making the mistake of comparing plasma to fire. A common mistake is to believe that a “red is less hot than yellow” or “blue is the hottest color”.
The reason this is the case with fire, is because the red-orange-yellow part of the fire is blackbody radiation emitted by the soot in the fire. Your body also emits blackbody radiation, but you need a thermal camera to see it.

However, the blue part of the flame is glowing because the hot atoms move from low- to high-energy states. When the atoms change back down to low-energy state, they release distinctive quantities (quantums) of energy, in the form of photons (light). The light emitted depends on the nature of the element, and thus different kinds of atoms will produce different colors of light. This is why burning copper can produce a greenish flame. Scientists use these physics to measure the composition of interesting materials, for example in metallurgy to analyze an alloy, or in astronomy to analyze the composition of stars.
More on this:

Stars emit light because of the fusion reaction occurring in them. Stars are plasma, and apart from the ongoing fusion reaction may serve as a good comparison for the plasma bolts seen in the Halo franchise.

In a given element, the distinctive quantum structure of the atom will release energy of a given pattern, in the form of light of a given wavelength. However, it is important to note that this does not say anything about the intensity of the energy. Thus, we can not gauge energy content or heat by the color of plasma.

This brings us to the actual Halo franchise, with the blue plasma bolt of the plasma rifle. Why is it blue? I’d say it’s first and foremost because blue is an ‘alien’ color, and fits the design language of the early covenant, but from a canonical point of view, I’ll hypothesize it is the most efficient energy-delivery system that the engineers (of several species) could put into a compact weapon platform.

It makes a lot of sense, then, that the Brute plasma rifle fires approximately the same bolts, but they glow a different color. During the story of Halo 2, the Elites were betrayed by the Prophets in favor of the Brutes. With the elites being given a cold-shoulder in the covenant internal affairs, it makes sense for infrastructure and logistics of their material flows to take a hit. At this point, the covenant is a massive multi-species allegiance in the midst of all-out intergalactic war with the humans. Much needed weapons are being mass manufactured, and suddenly the supply chain changes. In addition, the customer changes.

The original blue plasma rifle could be charged with energy and Xenon as the energy carrier/substrate. The wavelengths emitted by excited xenon-atoms create a distinctive blue color.

At the point of the Prophets betrayal, they could have easily shifted their supply chain towards other elements, like Neon or Cadmium, which can release a red color. -So it could have simply been by coincidence (canonically) that the brute plasma rifle fires red bolts.
To suit their tempers and battlefield habits, the new rifles were also made with a faster rate of fire, but were more easily overheated. As far as I know the individual bolts of blue or red plasma do the same amount of damage, which makes sense as explained above.

Now what about the Plasma Pistol? Well the plasma pistol is different for two reasons. Firstly, it has to be more economical, because it is the weapon given to less important troops like Grunts and Jackals (Jackals are somewhat proficient, but I understand them to be mercenaries? Please get back to me on that). And secondly, it has to be capable of firing a charged-up shot designed to eradicate energy shields. This presumably means the energy carrier that becomes the plasma has to be of a different composition. I hypothesize that the covenant uses a copper-based compound to create this plasma. Because copper is also highly conductive, potentially lending some credibility to the idea that charged Pistol shots can carry electromagnetic pulses over long distances. Copper releases green light by the mechanisms described above.

(Continued beneath).

Now let’s talk Energy Swords.
I always interpreted Energy Swords as being made out of something other than pure plasma. (Although 343 seems to indicate the opposite). Especially in the later games, you can see that the swords actually refract light, -sort-of like glass or crystal. Off course it would shatter if made out of glass so in my mind the Energy Swords in Halo are Covenant technology (primarily Elite) based off of Forerunner Hardlight.
Although in the case of the Energy Swords, the technology is not quite as refined as the forerunner version, thus “bleeding” off more light and appearing brighter, almost like plasma.

Now, as you know, the vast majority of energy swords seen in Halo have been bright blue-white in color. I think it makes sense for there to be only one color, especially since this weapon for the most part is a refined weapon especially crafted for Elite warriors. However, there have been some alternate colors that we should recognize before microtransactions go into double-rainbow mode in Halo Infinite.

The Arbiters own blade, the Prophets Bane, glows a yellowis-orange color. This makes a lot of sense because it is an ancient blade, -reforged with fragments of the sword that ended a prophet (in Halo 3). You know, it’s an elegant weapon for a more civilized age.
Being an older sword in design, the technology may have impurities inside the hardlight/plasma blade itself, and these impurities would release blackbody radiation in these colors (in the same way as they appear in normal flames). Based on the color, the forward points would be about 1300 degrees Celsius. This works by the same mechanism as the heated soot in a candle flame, creating visible light.

We will see red Energy Swords in the campaign of Halo Infinite. The background for these red swords is that they used to be employed by Elite Special forces, most notably a division called Silent Shadow.
The Silent Shadow division played a significant part of the Banished backstory, and several are likely to have joined or allied with the Banished.
Also, Halo Infinite concept art from this update shows the Elite assassin “Jega Rdomnai” with a red sword.

The decision to utilize red Energy Swords may have been a practical one in the eyes of the elites. Quite literally so, if there is truth to the theory that Elites cannot see the color red (needs clarification/confirmation), but also in the sense of conventional covert ops. This is because the wavelengths of red light can affect the eyes much less than other colors, and preserve the ability to see in the dark (at least for humans in the real world). Actual real-world military forces use red headlights, flashlights and info panels in cockpits to preserve night-vision. It makes sense for Elites to do the same if their eyes work somewhat similarly to human eyes.
More on that:

Canonically, the color adjustment of the sword blade could be handled/achieved the same way as with the plasma-bolts, i.e. by altering the chemical composition of the substrate which is consumed in the creation of the plasma/hardlight blade.
In conclusion, the introduction of red blades in Halo Infinite actually makes sense story-wise, in addition to fitting the overwhelmingly “hot-rod-red” color-scheme of the Banished faction.

Hopefully, there will be a semblance of canonical affiliation to the Energy Swords available in the multiplayer portion of the game when it launches in December of this year. The new business model, being based heavily on season-passes and microtransactions, can potentially bring some very colorful new additions to the game.
We have seen red blades in multiplayer before, in Halo 2 Anniversary in the infection gamemode (probably mostly to make it clearly visible that the player is infected); And in Halo 3 (MCC) Season 7, as described in This blog post. The latter describes the red (or most red-ish) blade as the Bloodblade of the Silent Shadow, implying that these are indeed canonical.

If I missed out on some canonical details, or if you have something to add, please don’t be afraid to share :slight_smile:

Excellent analysis, I was actually thinking about this not too long ago since I noticed the Banished seem to favor red plasma.

Great post, very informative.