Rosso and Blu still uses the trope of borrowing past Ultra Powers like their two predecessors but this time, they downplay it by using a single Ultra instead of two. But then it hit me: Orb and later on Geed are single protagonists of their starring shows who uses two Ultras at once for a single form, while Rosso and Blu are protagonist pairs of a singular series and two Ultras used a single past Ultra Power for each!.
Rosso and Blu's transformation call, "Color me with your power! R/B!" makes sense in that both Ultras' retain the color black and silver (in addition to Rosso and Blu's gold and silver bits) on their skin whereas the only changes went to their own armor. These Ultras are actually in need of new colors during transformation.
Meanwhile, Ultraman Orb Dark being all black and silver is not only portrayed as a grayscale (colorless) contrast to our color-changing protagonists. Remember that Orb is a parallel to Ultraman Tiga in many ways, and who else is an evil Ultra that bore the same coloration as Orb Dark? That's right: Tiga Dark.
Someone in Pixiv pointed out that combining the first nouns of Minato siblings (Katsumi, Isami and Asahi) into Kaia, and the Minato parents instead (Ushio, Mio) into Umi. Kaia is one letter close to Gaia and Umi is the Japanese word of sea, which was Ultraman Agul's attribute. This makes a nice tribute to the 20th anniversary of Ultraman Gaia.
All crystals that Rosso and Blu uses are Taro (Fire), Ginga (Water), Tiga (Wind) and Victory (Earth). They are all known for being associated to Ultraman Ginga and his host in one way or another:
Taro: He mentors Hikaru and provides Ginga with Ginga Strium.
Tiga: He is the alternative for Hikaru to transform against Tyrant at one point (and unlike all Spark Dolls, Hikaru succeeded with Jean-nine's help).
A lot of fans express their displeasure when Ultraman Ginga was picked as the representation of the element "water" instead of Ultraman Agul (who in Gaia is the Anthropomorphic Personification of sea), but suddenly it all makes sense: a) Its been five years since Ginga first aired and since its the first Ultra Series to air after 3 years of Ultraman Retsuden, so honoring the former Ultra series would be nice b) Rosso and Blu as a red and blue Ultra duo is already a Gaia and Agul tribute, so if Agul becomes the representation of water, Blu's resemblance to the former would be too obvious and c) The fact that Rosso and Blu uses Taro and Ginga's crystals would as well provide a stealth meaning: Rosso's human host is an older brother who always look after Blu's human host, just like how Taro would provide guidance to Ginga's host Hikaru during Ginga and Ginga S series run.
The series confirms that Rosso implemented Katsumi's baseball skills in Energy Ball attacks. So why does Blu fires stream of elemental energies? Simple: back in episode 2, Isami is the only one who is eager to to fight as Ultraman whereas Katsumi falls into With Great Power Comes Great Responsibility. He is an embodiment of a kid who wants to be hero and becoming one is like a wish come true. When he stretches his arms forward to unleash Kamehame Hadoken elemental attacks, he is basically having the thoughts of standard main characters of shonen genre Anime and Manga.
Orb Dark complains that recent Ultramen are prone to talk a lot during battle. If one were to look at the finishers his Orb Ring Neo supplies, it lacks those of Hurricane Slash, Lightning Attacker, Emerium Slugger and Orb Trinity. Hurricane Slash's is justified since Orb Dark has no way of replicating attacks without a copy of Orb Slugger Lance, but speaking all of these excepted powers as a whole, they contain New Generation Ultras, whose the subject of Orb Dark's earlier rant.
Why does the Orb Ring NEO is the simplest transformation device when compared to Rosso and Blu's Gyro? Aside from marketing purpose, it fits Makoto's Nostalgia Filter of past Ultramen.
Plus, Orb Dark is a ripoff of Orb Origin and Origin the First, both of which can use the Orbcalibur solely without reliance of other collectible devices.
In episode 3, the petrified bird who falls onto Makoto's head was indeed the work of Gargorgon. If her main eye was damaged, anything that's petrified returns to normal, but that fallen bird had its left wing broke during the fall. Chances are, it would instantly die when the power worn out or the bird wakes up in agony that its left wing broke.
Let's discuss about Makoto's entire time of being possessed by Chereza. The gaseous alien is said to have been on Earth for 15 years, almost the same period of Mio Minato's disappearance. Of course the real Makoto went traveling abroad with his bicycle; his entire time of being possessed would have make him a Fish out of Temporal Water, so by any chance, he may have missed out a lot of major events and changes. Not to mention, he was possessed since his age of 18 years old and may have missed out a good portion of his adulthood.