The Starlights fuku appeared in the fifth and final season of the series, as well as the final arc of the manga. The fuku are the same in both versions and the Starlights wear nearly identical uniforms, most likely to symbolize that they were a team instead of acting as individual Sailors (such as Galaxia and Heavy Metal Papillion, for example).
The Starlight fuku are perhaps the most notable to be the first with a bottom part that didn't involve a skirt and to be made out of a different material than the fuku we have seen before. The Starlights wear shorts (perhaps more accurately "hot pants") and bikini tops. The fuku blends the dual identity and gender of the Starlights. As the Threelights, the women disguise themselves as men. Shorts are typically viewed as masculine clothing in comparison to skirts, which is the norm for sailor fuku. The bikini tops are most certainly feminine, so the combination of the shorts and bikini top accurately represent the Starlights.
According to the Alex Glover translations of the Materials Collection the fuku material is enamel. It's jet black and shiny, invoking a futuristic and (coupled with how little the fuku covers the body and the many straps and belts) feels a bit dominatrix. With the Starlights' general superior and cocky attitude, the fuku conveys strength and superiority.
The main fuku color is black. Black has several symbolism depending on the country and context in which it is used. It can mean power, sexuality, sophistication, and wealth. It can also mean mystery, evil, sadness, and mourning. Because of the structure of the fuku and the history of the Starlights, I'm inclined to assign the traits of power, sexuality, mystery, and mourning in this context. As I wrote previously, the design of the fuku evokes a sense of dominance and sexuality. The Starlights appear to have and believe they are more powerful than the Sailors on Earth, so representing that as a main color on their fuku is a perfect visual representation and neatly drawn line between the two groups. Using black also provides contrast between the Sailor's white (represents purity, peace, and innocence) bodice fukus, which may indicate that the Starlights are less pure and/or innocent than them.
It may also be interesting to point out that in Eastern culture white represents death while in Western culture it is black that represents death. If we keep in mind that the Sailors of Earth chose to die for their planet to protect it while the Starlights fled Kinmoku in order to find their princess, we may be able to apply the Eastern symbolism of the colors. However, the Starlights' fuku may also represent the death of their planet, which is in alignment with the Western representation of the color.
In terms of mystery, the Starlights appear seemingly out of nowhere and refuse to provide assistance or join Usagi in her struggle in protecting her planet. The fact that as the Threelights they hide the gender makes it further difficult for any of the Sailors to identify these strangers to their planet. The introduction sequences in the cartoon lends towards the idea of "shrouded in mystery" as they appear from the shadows, only revealing themselves with spotlights.
Mourning is an easyconnection to make. Kinmoku was attacked by Galaxia and the Starlights left their planet to die in hopes of protecting Princess Kakyuu. They mourn the loss of their planet as well as their princess as she has gone missing.
The star shape is heavily connected to the Starlights. The shape is used for their transformation items, brooch, and various pieces of jewelry. The easiest connection to make is that the star represents the alien status of the Starlights. They comes from a different planet, literally from one of the many stars seen in the night sky. The star shape culturally refers to fame. As the Threelights they become famous pop idols and their transformation device is involves the use of a headset.
The star shape is often used by militaries. As we do not know much about Kinmoku aside from the planet having a single monarchy, it is possible that the Starlights' duties extended beyond being Kakyuu's personal protectors and perhaps also headed the military forces of the planet, similar to how the Inner Guard were shown to also protect the Moon, not just Princess Serenity, when the Silver Millennium was attacked by Queen Metallia.
Stars also represent the heavens. This plays directly with the wing motif found on their brooch and headset piece. The Starlights literally descended from the stars, or the heavens, onto Earth. As we often associate white feathered wings to angels, we can extend this symbolism to the Starlights as they are guardians of their planet and princess, eventually also becoming protectors of Usagi during their stay on Earth.
Sailor Star Fighter: In Detail
Fighter's image color is described in the materials collection as navy blue and she is drawn with almost powder blue accent colors on her fuku. Dark blue colors, such as navy, represent intelligence, stability, unity, and elegance. Navy blue is specifically named after the color used for the British Royal Navy. Blue in general represents loyalty, importance, and confidence. Most of these definitions represents Fighter in some way as the leader of the Starlights and her confident and loyal demeanor. Although Naoko originally intended navy blue to be her image color, Fighter is drawn with powder blue accents. However, there is actual significance in combining shades of dark and light blue ("banker's colors"), and they represent trust and truthfulness. As Seiya, she gains Usagi's trust and is committed to telling Usagi the truth about the Starlights and what happened to Kinmoku.
Sailor Star Healer: In Detail
In the Materials collection Naoko writes that Healer's theme color is gray. However, she makes several notes of Healer and Yaten wearing bright green in their accessories, this carries over in Healer's fuku which is trimmed in yellow-green. Gray may symbolize Healer's mental state, which is grieving the loss of her planet and princess. Unlike Fighter who remains positive and dedicated to their mission and Maker that has become complacent, Healer's sadness comes with anger.
In many ways, green also represents her sadness. Green can represent jealousy, misfortune, and vigor. Healer displays these emotions internally and outward, to her teammates and to those she finds offensive. Healer's eyes are green, which in the west represents jealousy. This could also be applied to Healer as she appears envious of those who haven't lost what she has and the pain she is going through. However, green also represents renewal, youth, and generosity. We see her display kindness towards Luna, and after understanding Minako's motivations for becoming an idol, to her as well. Healer is based on Vishnu, the Hindu god called "the maintainer or preserver" that is often tied to nature. Although Vishnu is represented by the color blue, green equally represents nature.
Sailor Star Maker: In Detail
Maker is in the same position as Healer where Naoko assigned her image color as light brown, but she is depicted in purple on her fuku. Brown represents stability, hearth, and earth. It's likely that the colors is meant to tie directly to what her name, Maker, implies. Maker is also the most level headed of the trio, as well as the most reserved. Purple represents spirituality, wisdom, enlightenment, arrogance, and mourning. Like her teammates, Maker is deeply affected by the loss of her homeworld and princess. However, she remains complacent, rarely emoting her distress, which may be the result of her more analytical and wise nature. She is also rather arrogant, believing herself and knowledge to be superior to those on Earth.
Maker is based on the Hindu god Brahma, the creator. The color purple in terms of spirituality and enlightenment may refer to her ties with Brahma. Maker's name and her attacks seem to apply towards reproduction, specifically female, and may also imply a wise mother figure. The hearth (brown) and wisdom (purple) may represent this.
In Naoko's early drawings and some of the colored art, Maker appears to be wearing more of a pink shade rather than purple. Pink doesn't really seem to suit Maker, so perhaps Naoko intended to make her more feminine to allude to Maker's name and attacks or perhaps she had a different personality.
