Android Identifier

The effect was so convincing, so real, that all holograms bore a two-inch high, metallic-looking 'H' on their foreheads, so they could never be mistaken for living people. The stigma of the dead. Not the mark of Cain, the killer, but the mark of Abel, the slain.

— Red Dwarf: Infinity Welcomes Careful Drivers

In a world where humans live together with completely human-looking androids, artificial humans or clones, there may be a need to keep them visually distinct from real humans in that society's eyes. They could be purposefully designed with unnaturally colored features, such as hair, eyes or even skin, or given a tattoo, marking or barcode. In other cases, their features are kept completely human, and their artificial status is shown through a special uniform or insignia.

This could just be a visual shorthand for the viewer to quickly identify which societal group the character belongs to (with headset like ears being a common identifier). Especially in live-action properties, it can be easier to give actors colored contacts or distinct clothes instead of a more involved and costly robot look, similarly to Rubber-Forehead Aliens. Since androids in fiction are rarely allowed to both look human and act human, an Android Identifier also serves the Doylist function of both allowing the character to act more human and still be immediately recognized by the audience as artificial.

On the other side, such an identifier is also often used to showcase the Fantastic Racism in such a society with an Androids Are People, Too or Clones Are People, Too plot. If it's not done subtly, expect armbands or badges reminiscent of real-life oppression like the yellow star of David. This trope may lead to at least one Robotic Reveal when an artificial human has removed or hidden their identifier to go on the run or blend in.

Sub-Trope of Group-Identifying Feature. This can also be combined with non-visual identifiers, such as Machine Monotone, Robo Speak and Robot Names.

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Examples:

Anime & Manga

• Chobits: Persocoms have metal protrusions instead of normal ears and occasionally unusual hair colors, but they look and can act like humans otherwise. The ears do also have a practical function (to plug in wires), but don't seem to be necessary, as some models like the custom persocom Yuzuki don't appear to have them.
• In Extreme Hearts, robots are made specifically to help athletes practice and fill player quotas. These robots all have silvery-white hair and blue or gold eyes, which seems to be a combination that doesn't happen for regular humans among the cast. Downplayed, as it seems that it only applies to these specific sports robots. The housekeeper and manager robot, Nono, looks completely different.
• In Metallic Rouge, many Neans have conspicuous physical traits which mark them as androids at a glance, such as inhuman eye colors and skin tones, circuitry patterns on the skin, or obvious mechanical components. Other Neans lack these traits, however, and can pass for human as long as they keep their Nectar injection ports hidden.
• In Negima! Magister Negi Magi, Chachamaru as well as her sisters are identified by their large robot ears. Chisame is the only person in class 3-A who seems to notice these, and remarks on how weird it is to have a robot in their class. Everyone else doesn't notice or just doesn't care.
• In Time of Eve, humanoid robots are required by law to wear a holographic ring over their head resembling a halo to distinguish them from humans. The titular cafe is a place where no distinction between humans and robots is made, therefore, robot patrons turn their halos off to blend in.

Fan Works

• Mega Man: Defender of the Human Race: Federal law requires robots with human forms have a distinguishing physical feature. This is the way the story explains why Rock has his blue armored legs before becoming Mega Man.

Films — Live-Action

• In Blade Runner, the Nexus models are so lifelike, a special empathy test (Voigt-Kampff) is needed to properly identify a Replicant and retire it.
• In Cloud Atlas, Fabricants wear colored streaks in their hair as a visual identifier of their status. Fabricant Sonmi~451 cuts off her streak in rebellion.
• In Westworld, the robots of Delos Park are very close to resembling humans, except for having silver eyes, a lower body temperature and notably less human-like palms on their hands. While the palms are In-Universe Technology Marches On concerns (two of the park's guests discuss that the technicians are still working on getting them right), both visual details are still used to identify (and thus reassure) that someone isn't a robot at two different points of the film.
• Zygote: Synthetics are created by Mega Corps to work dangerous jobs such as Asteroid Mining. Synthetic humans like Barklay have a barcode to mark them as such. Subverted when it's revealed that creating synthetics is expensive, so human orphans are often used instead and tattooed to fool inspectors.

Literature

• In Beta, clones are essentially used as a disposable servant race for the mega-rich. Their beauty is enhanced in the process, and they are given luminous fuchsia eyes and a tattoo on their right temple to tell them apart from their owners. The main character is a teenage Beta and like all of them also sports a purple BETA on the back of her neck to mark her as a prototype. It is shown that clones are otherwise identical to humans when Tahir is revealed to be a clone posing as his original who died in a surfing accident.
• In Friday, Artificial People — genetically engineered lab-created humans — have lesser rights than "natural-born" humans and are required to have identifying tattoos. Friday herself, being a covert agent, had hers removed.
• In the Hyperion Cantos, androids — which are not machines, but rather (mostly) organic Artificial Humans — have bright blue skin to better distinguish them from normal humans.
• Liaden Universe: In the prequel duology, Batchers are an underclass of artificial human servants who are marked by glowing green markings on both arms, which they're required to keep visible at all times. Though usually referred to as "tattoos", the markings are genetically expressed and can't be removed by any of the methods that would work for a normal tattoo. The only method widely known to work is to amputate and regrow the entire arm (the setting's medical science include limb regeneration), but even if a rogue Batcher could find someone who they trust to perform the operation, a person who's "lost" both arms will inevitably attract suspicion.

Live-Action TV

• Androids in Humans look exactly like humans except for their unnaturally colored and/or super vivid eye colors. Going undercover as a human is possible using colored contacts and is done by the rebelling protagonists.
• Kamen Rider Zero-One: Humagears (see page image) are Hiden Intelligence's premier worker robots. They have special Humagear Modules on their ears to distinguish them from Humans as well as Body Seals (essentially bar codes) on their upper bodies should they need to be scanned. Barring a few exceptions, these Modules are normally blue — they turn blood red when the Humagear is hacked into a homicidal Magia by Metsuboujinrai. Notably, as a sign of rebellion, Horobi and Jin ripped their Modules off, showing a clear defiance of the rules imposed on them by humans.
• Red Dwarf:
  • Holograms (hologrammatic A.I. simulations of dead people) have an "H" badge on their foreheads, since otherwise, they could be mistaken for living people. The tie-in novel Infinity Welcomes Careful Drivers describes it as "the stigma of the dead".
  • Mechanoids are usually designed with blocky-looking, obviously artificial faces. It is revealed in one episode that androids that could be mistaken for a human were once made, but were discontinued because people found them uncomfortable to interact with.
• Space: Above and Beyond: The Artificial Humans called "InVitros" do not have belly buttons, but rather nipple-like bumps on the back of their necks from where artificial placentas were attached to them in their womb-tanks (hence the Fantastic Slurs "nipple-neck" and "tanks").
• Star Trek:
  • Star Trek: The Next Generation: Soong-type androids like main character Data and his Evil Twin Lore are constructed with metallic white-golden skin and yellow eyes. As completely human looking androids did already appear in Star Trek: The Original Series, set almost a century earlier, this seems to be a deliberate design choice to make them stand apart from humans. This is further cemented when Data is able to provide his daughter with "more realistic skin and eye color", and later when an android replica of Dr. Soong's former wife shows up — she has human skin and eye color, seems to be technologically more advanced than Data, and she is unaware of her nature.
    • Brent Spiner, finding his makeup process arduous early on in TNG's production, asked the same question – "If you could make a creature that moves like this and looks like this and thinks like this, why can't you do the skin?", to which Gene Roddenberry replied, "What makes you think what you have isn't better than skin?".
  • In Star Trek: Picard and the Short Trek episode "Children of Mars", non-sentient androids are used as manual labor. They have the same golden-white coloring as Data, are all bald and have an identifying number on their forehead. During the first season of Picard, multiple Soong-type androids appear — while most of them are designed to blend in among humans and thus look identical to them, some retain variations of the trademark Soong gold coloring.

Tabletop Games

• Pathfinder: Androids look almost exactly like humans except for slightly metallic eyes and faint circuit-like patterns in their skin, which glow when they activate their nanite surge. They also have clear Machine Blood.

Video Games

• In Detroit: Become Human, CyberLife androids have glowing LED rings on their temple and wear clothes with glowing triangles and "Android" nametags to keep them apart from humans. The rings have a dual function of signaling the Android's emotional state, but the clothes are purely aesthetic. Androids on the run or in hiding, like protagonist Kara, remove their rings and change clothing to blend in among humans. Child androids or androids replacing family members seem to be exempt from this, as shown by Alice being revealed as an android.
• In Digital Devil Saga, A.I. characters are signified by unnatural hair and eye colors. Given that their creator designed the first A.I.s to otherwise look exactly like people she knew, it's possible that it was to avoid confusing them with each other.
• Inazuma Eleven: The members of Perfect Cascade from Chrono Stone are androids with two modes: Practise and Hyper Dive. In Practise Mode, they look like normal humans with very pale skin. In Hyper Dive Mode, they gain black lines on their faces and black visors.
• Mega Man ZX is set in a future where humans and Reploids are indistinguishable from each other, with the former augmenting themselves with robotic implants and the latter developing more finite lifespans. As a result, to be able to distinguish the two, Reploids are given a bright pink triangle on their foreheads. Interestingly, in Advent, you can meet a Hunter named Nick who doesn't have the triangle. He explains that he's an "old-model" Reploid who still has a finite lifespan but is more noticeably robotic (having a more armored upper-body and obviously mechanical hands that according to official art have blasters in the fingers) than other Reploids.

Webcomics

• Forward: Building a robot that could be mistaken for a human is illegal. Robots are allowed to be vaguely humanoid in form but a large number of specific design features are forbidden, such as five-fingered hands.
• Megatokyo: Androids of Ping's series have large plastic "earrings" that include digital readouts and connection ports.
• Never Mind the Gap: Artificial intelligences are (or were) required to show a "blue tear" first on their forum avatars, then on their physical bodies.

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