In fiction, if you run into someone who looks like a corpse, it's not that they're sick, it's that they're dead.
Characters who become one of The Undead will develop pale or sometimes blue or green tinged skin. In severe cases with visible (and deathly still) purple veins underneath the skin. Even people of color* who were dark skinned in life will have it turn ash grey, or dark like soot.
A living character who is just pale is usually a perfectly mundane case of an Eerie Pale-Skinned Brunette, who has heard all the jokes about waking up on the wrong side of the coffin. There may be some Unfortunate Implications here though, since in fiction there's a strong correlation between being pale and going over to The Dark Side. In addition living characters who come into contact with the dead, undead, or infernal may have a change of color and become Hades Shaded. This is the case with necromancers, infernalists, those under ghostly Demonic Possession, someone bitten by zombies or a vampire, or The Renfield who has fed on vampire blood. It doesn't stop there either, centuries of sunless existence may turn the character into an Evil Albino.
This trope is so common it's usually a dead giveaway that something is wrong with Alice / Bob when they suddenly show up this shade of pale. Smart characters (let alone the Genre Savvy) will have their Not a Zombie sense ping them as being "somehow off". Which of course makes the defiance of this trope a #1 priority on every smart undead's list of Masquerade reinforcing tricks. Settings where this trope is subverted have much more dangerous undead for being indistinguishable from the living. Another curious exception is that sometimes people who were brown-skinned or darker in life may look exactly as vivid after death as they did when they were alive for unexplained reasons. Probably something to do with the Special Effects budget and wanting to avoid a gaffe.
Truth in Television, as once you die, the blood moves due to gravity to the lower parts of your body (if you are lying on your back, then it pools there). It's called Post-mortem lividity. So if your skin looks drained of blood, it's because it is.
- Sid from Soul Eater is a zombie gym teacher. He once had normal colored skin, but after dying he became blue... Literally.
- Owl / Seidou Takizawa from Tokyo Ghoul:Re is not undead, but makes use of this trope as part of his overall Zombie motif. In colored artwork, he's almost as pale as his white hair, with sunken eyes and discolored lips and nails. At one point, he talks about himself as someone that has already died and has a taste for brains.
- Dead Girl in X-Statix, who's sort of greenish.
- Any Black Lantern who didn't just have a skull for a face had grey skin.
- Malibu Comics' Ultraverse character Ghoul was green (and pretty messy besides).
- Subverted in Death Vigil; it's a side-effect of the Reaper's scythe to make its wielder have Mystical White Hair and pale skin—the appearance isn't unique to the Reaper herself.
- Lady Death is an undead sorceress and milk-pale. In the Avatar Comics, there is a term for people that are sentenced to the Labyrinth called "albinos", whom had willingly performed deals with the dark specters that rule it and become undead beings of extreme power, but hated by others.
- Dark City - The Strangers are alien energy forms who inhabit human corpses as a means of performing routine physical actions.
- Corpse Bride provides the page image here, though it's played with by having the living be colorless while the dead have much brighter colors.
- The alien monster mutants in Pandorum are all Undeathly Pale. It's later revealed to be because they evolved and mutated over centuries to become apex predators for the ship they inhabit by feeding on the other passengers of the ship.
- The Morlocks in The Time Machine have a similar reason for their pallor.
- Twilight plays this trope straight with caucasian vampires, but Laurent presents an odd contrast. He's not at all pale in the first movie, but was washed out and greyish though, at least in the second film.
- Drac and the female vampires in Bram Stoker's Dracula. While he doesn't display it in his younger form, his older form has has very pale skin. His brides have it though the dark lighting of their scenes make it hard to tell. Lucy on the other hand goes completely deathly white after turning.
- Vampires in the original Buffy the Vampire Slayer movie had this among other mutated features to show they weren't human anymore.
- Count Yorga when he goes full vamp mode to really show off his monstrous form. Likewise the vampires under his control.
- In the film commentary for The Fellowship of the Ring, Peter Jackson discusses how Boromir's skin was paled just a little bit at the moment he succumbs to his wounds and dies. The change is so subtle that most viewers might not consciously pick it up, yet still provides his death scene a little extra punch.
- In the Twilight books, Maria the vampire looked "porcelain" despite being Mexican. The book is pretty inconsistent about what happens to People of Color when they become vampires. Maria was really pale and Laurent was olive-skinned (but it was never stated what race he was). There are some other vampires who are non-Caucasian, but their skin color isn't really mentioned. The male half vampire from South America was definitely dark skinned, though.
- Variation in the Old Kingdom series. The actual Dead aren't noted to be pale (since most of them that actually have physical bodies are too badly decayed to tell) but Necromancers (as well as Abhorsens, who practice necromancy to destroy, rather than create or control, the undead) are described as noticeably paler than those who don't practice that art. So it's pallor from associating with death and the undead, rather than from being dead yourself.
- In Warbreaker, when a Lifeless is created, all color is bleached from their body as a side-effect of the magic (which uses color as a sort of trigger). The resulting creatures look exactly like they did in life, except that they are pale grey all over.
- When Kairn becomes a zombie shortly after dying in Galaxy of Fear: City of the Dead, Zak thinks he looks sallow-skinned and unhealthy like he's been sick, not like the rotting zombies in his dreams.
- This is why zombie rights activist Reg Shoe in the Discworld novels sports a "Glad to be Grey" badge.
- In Quazi, the titular intelligent zombies and the feral Risen (who haven't yet regained intelligence) eventually develop bluish-gray skin that sharply distinguishes them from the living. They're not really dead, though, and actually have a pretty good Healing Factor, although it works fairly slowly.
- Miss Persephone Parker in the The Strangely Beautiful Series is so pale that she's often mistaken for a ghost.
- Game of Thrones: Gregor Clegane's skin seems to be a pale purple, likely a result of congealed blood and/or partial decomposing.
- All the zombies in In the Flesh look white and their pupils in their eyes look like crosses. They wear make-up and contacts to appear like the living.
- In the Supernatural episode "What Is And What Should Never Be", this is a Subverted Trope. Sam finds Dean and the woman in white hanging limply with pale faces and unblinking red-rimmed eyes, but they both survive.
- The vampires of Forever Knight, except for the handsome Vampire Detective protagonist. In the pilot episode, his tan is handwaved by Nick Knight saying he was exposing himself to the sun for limited amounts of time, as part of his ongoing attempt to cure his vampirism. Later episodes have him using a sunbed.
- The zombies of iZombie become noticeably pale with bleached out hair. At least one zombie deliberately dyes his hair to conceal this.
- The Abyssal Exalted get this in spades - As they get more powerful, Abyssals are required to either become pale (if they were light-skinned in life) and beautiful, or decayed and monstrous. As a high Appearance Abyssal's colors change towards the natural extreme they are closest to, Abyssals who were dark-skinned in life invert this trope, with skin colors resembling obsidian.
- In both Vampire: The Masquerade and Vampire: The Requiem, vampires typically grow paler and less lifelike as they grow older — not because of age, but because an older vampire is more likely to have fallen a few notches down the Humanity scale and gotten closer to their Beast. The one exception may be the Assamites from Vampire: The Masquerade, who invert the trope by growing darker as they age, to the point where the elders of the line look like they're made of polished jet.
- The Cappadocians, a clan-turned-bloodline in Masquerade take this a step further. They always appear corpse-like, unable to use Flush of Life to mask their pale faces regardless of age or humanity score. When they get older, they grow even more like wasted cadavers. The Harbingers of Skulls (Cappadocian survivors), due to their time spent in the Underworld, are outright dessicated corpses.
- In World of Warcraft the Forsaken have skin in various shades of grey, green and blue. Death Knights also tend to be paler then a living character with the same setting of skin shade. They also have access to a several different skin tones not available to living players, mostly in greens and greys. Though some of them are a bit odd - blood elves apparently decay into charcoal.
- Brütal Legend has the Drowning Doom, whom all their units have this look to them. Most noticeable is Drowned Ophelia, the doppelganger counterpart of Ironheade's Ophelia, who, naturally, turns from a healthy looking, yet slightly pale Perky Goth, to an openly corpse blue after her transformation into the Queen of Black Tears.
- In Gaia Online, the main zombie skintones tend to be gray-white or greenish, though alternate zombie skintones have been known to include dark blue, purplish, and bright scarlet. There are four vampire skintones as well; a crappy 100 Gold potion in Skin Tyte with an exclusively pale-white base, and three found only in The Treehouse and the marketplace, which range from "basically, we just improved the old skintone" to "Now you, too, can be Ambiguously Brown". Zhivago in the plot manga and Kamilla in zOMG! are also Ambiguously Brown vampires, and were rather famous for formerly being the only ones.
- The Sims 2 does this. Zombies are gray, vampires are blue. However, as with most things in The Sims, custom content exists to change these.
- Also, in some MySims sequels, beginning with MySims Kingdom, Carl the Zombie is blue, with rotted away hair. In MySims Agents, his arm even falls off.
- In The Sims 3 Supernatural expansion, all the premade ghost characters have blue skin, hair and eyes, although they show up in game as different colors depending on what they died of.
- In the Kingdom Hearts series, Sora will have white skin whenever he is in Halloween Town as a result of becoming a vampire. He's not really undead. He retains the skin color in Christmas Town, where he wears a black Santa Claus jumper and hat over his clothes and eyepatch, respectively.
- In Castlevania: Lords of Shadow 2, Dracula's skin became bone white after centuries of vampirism.
- Queen Frieda of One Way Heroics has slightly paler skin than the non-undead party members. It might be a case of this trope, but it might also just be a case of the lighting on her character portrait.
- Zombidle: Bob the Necromancer, as well as the Zombie Horde, Giant Zombie and The Big Plague all have deep green skin.
- Metal Slug 3's zombies in the second mission have grayish-blue skin, and if the player or the various injured civilians around the area get zombified from a Zombie Puke Attack their skin changes to match.
- Frédéric Chopin in Frederic: Resurrection Of Music has bluish white skin due to being undead. He gains a more normal skin tone in the final level.
- In Zombie Ranch people turned into zombies become noticeably green. Other mammals just seem to go green on the inside.
- The Kingfisher: Pale vampires abound.
- Being based off of Exalted, Keychain of Creation features various extremely pale Abyssals, the best-known of which is, of course, Secret.
- School Bites: All of the usual vampires have chalk white skin, save Cleobatra who's African American but still sports a bit of paleness.
- Camille in Bloody Urbanhas very light blue skin, despite the fact that she is of African descent. Recent comics show it changes back to its original pre-death color when she drinks blood.
- The zombie twins Hex and Mye in Charby the Vampirate have very pale skin as do most of the vampires.
- Strangely inverted by Danny Phantom, whose skin when he's a ghost is actually more tan than it is when he's human. Possibly this was done to have a stronger color contrast against his white hair. In contrast, the skin of Vlad's ghost form has a more typical pale blue shade.
- Lydia Deetz in Beetlejuice is rather pale-skinned.
- Weirdly played with in Steven Universe: Lion turns out to have come Back from the Dead with his body altered to a state that in some ways resembles the undead. The same eventually happens to Lars. Both have their skin and hair turn a shade of pink much paler than they were naturally.
Answer: You actually checked? Wow, okay. It's Emily, the girl on the right with the boney arms.