Rex had previously welded his old Phase I clone helmet with Phase II helmet, giving him a truly unique look. This means the bottom part of his helmet is different from the top half; it also means that while Rex matched none of the other clones, his helmet also had something in common with every clone's helmet.
In "Darkness on Umbara", Anakin describes Rex as his "first-in-command" and second-to-none in loyalty or capability. Rex's later helmet design (right) is a hybrid of his original helmet (left) and the regular Episode III clone trooper helmet (center).
Turns out, they were on Joe Johnston's original Boba Fett armor concepts; and later expanded as “jaig eyes”, a Mandalorian emblem that “represents the eyes of a shriek-hawk”2 and is awarded to Mandalorians- and later Clones- as a mark of honor for acts of great courage.
Rex's helmet, which he wore in the latter half of the war, was a modified combination. of both Phase 1 and Phase 2 clone armor, which we explained in a recent video. As other clones transitioned to standard Phase 2 gear, Rex welded his new and old issued armor. into his own hybrid.
To sell the deception, they created a false grave for Rex, and buried a random clone in his armour. I assume this is why Rex's helmet changes in Rebels. It is in fact, not his original helmet, but a second Phase II helmet he cobbled together later on, this time using less Phase I parts (only the visor).
During the Clone Wars, several clone troopers bore tally marks on their helmet to signify their kills. Captains CT-7567 "Rex" and CC-5576-39 "Gregor" were some clone officers that possessed tallies, however Rex stated he didn't keep track. Other troopers that had tallies included Waxer and Buzz.
Jaig eyes—a simplification of jai'galaar'la sur'haii'se, translating as "shriek-hawk eyes" in Mando'a, and more commonly referred to simply as jaig—were a Mandalorian sigil bestowed by clan leaders as a mark of honor, awarded for particular acts of bravery.
It is a symbol of battle honor to Mandalorians. Rex painted them on his helmet himself. The blue symbols on Rex's helmet are Jaig Eyes. This is short for jai'galaara'la sur'haii'se, which means “shriek-hawk eyes” in Mando'a [the language of Mandalorians]. They are a combat honor.
Okay, so both Boba and Jango Fett have head spires on there helmets, which act as targeting systems for the rockets on their back. Why don't Din Djarin or any other Mandos have them? Din has a newer built in computer system that does that and more. The scope is an attachment thatmost Mandalorians do not possess.
Kamas (or belt-capes) were skirt-like armor accoutrements worn from the belt. In the later days of clone trooper Phase I armor, Clone Commanders, Clone Captains, clone commandos of Clone Force 99, and Advanced Recon Commandos added blast-resistant kamas to their kits, along with other gear.
Since Tano no longer held an official position in the Grand Army of the Republic after leaving the Jedi Order, Rex was formally placed in command with Tano serving as a civilian advisor. Despite this, all of the clones, Rex included, deferred to her and painted their helmets in imitation of her facial markings.
Despite his customized armor that greatly resembled that of an ARC Trooper, Rex was a standard Clone Trooper with the rank of Captain. This means that Rex was heavily modified from the Jango Fett template like the majority of Clones and underwent conditioning meant to make him totally obedient.
Rebels producer Dave Filoni fueled the speculation by stating that it was indeed possible the old man was Rex given that the series finale mentioned Rex as having been at Endor. Filoni later decided that the old man who appeared on film was the previously identified Nik Sant.
Anyway, in answer to your second question, Rex is not a Mandalorian. His armor bears a resemblance to Mandalorian armor, however, because the clone template Jango Fett wore Mandalorian armor, and the armor of clone troopers was based upon Fett's.
The leader of the 501st Legion's Torrent Company, CT-7567 – better known as Rex – was an exemplary clone trooper, brave under fire and dedicated to the men serving under him. As a no-nonsense, by-the-book trooper, Rex had to adjust to the maverick Jedi General Anakin Skywalker and his headstrong Padawan Ahsoka Tano.
Each Jedi Master or Knight that has the rank of “General” is given a legion of clones. The blue-striped soldiers of the 501st serving under Anakin, like Captain Rex, wear blue; the orange-striped soldiers of the 212th serving under Obi-Wan, like Cody, wear orange.
A: Captain Rex modified his suit. He did not like the phase 2 clone trooper armor as much so he welded the phase 1 chest piece and the phase 1 T visor to fit his needs. That's why there are orange marks on his helmet and chest.
Clone Captain Rex (CC-7567/CT-7567) was an Elite (later Veteran) Clone Officer who served in the 501st Torrent Co. clone battalion under the command of Jedi General Anakin Skywalker, Jedi Padawan Commander Ahsoka Tano, and Admiral (later Captain) Wullf Yularen.
Commander Wolffe's alternate Phase 1 helmet was originally an "easter egg" hinting the transition to Wolffe's Phase 2 helmet design for Season 4 during the Clone Wars Season 3 finale episode "Padawan Lost". Wolffe often disliked C-3PO and R2-D2, for he was often annoyed with how C-3PO often talked endlessly.
Because otherwise the other clones wouldn't recognise him. It's the markings on his helmet that make him unique from the other clones to show superiority.
In the promotional materials for Star Wars: The Bad Batch Season 2, the team finally has new garb -- which may be a sign that they are further adapting to their new life. Their uniforms now seem to include multiple materials and colors such as red, gray, tan and an orange-gold color.
