This is something of a logical counterpart to Common Eye Colors: If a character has freaky, cool, or otherwise unusual hair colours, their eyes are liable to match. "Unusual", of course, needs to be taken with a grain of salt when it comes to Anime Hair. Comic books and western animation are also likely to display this trope.
Some series use this to make a character stand out as being "weird" or "different", especially if it's an uncommon color. Others use this for their entire cast.
May be used as a form of Technicolor Eyes.
Not to be confused with the carpet matching the drapes.
Just about every character in the Fruits Basket manga, except the characters with black hair, who have dark gray or dark brown eyes, and the natural blondes, who have brown eyes.
Quite a few characters in Pokémon, be they lifted from the games or anime-original characters.
A great deal of the cast of Sailor Moon matches this trope. Of the heroes, Chibiusa, Ami, Michiru, Rei, and Hotaru. And in some artbook pictures, all of them do, including Sailor Moon herself. Of the rest of the cast, all of the Witches Five, several of the Anima-Mates, and Princess Kakyuu.
Dijiko (green eyes and hair), Puchiko (brown hair and eyes), and Hikaru (pink hair and eyes) from Di Gi Charat
Edward Elric from Fullmetal Alchemist. His amber-colored eyes match his blond hair. Alphonse and Hohenheim also share this trait, since this is a trait of all people from Xerxes.
The Tokyo Mew Mew girls in their Mew Mew forms (and all the time in the manga). Except Berii, 'cause she's special.
In the anime Haunted Junction, a large number of characters have hair and eyes the same color, including two out of the three leads.
Lina Inverse of the Slayers fame is a red-eyed redhead, and Xellos is purple-haired with lavender eyes.
Hikaru and Umi from Magic Knight Rayearth have red eyes/red hair and blue eyes/blue hair respectively. Originally, the third of the trio, Fuu, was going to have green hair to go with her green eyes, but the artists decided on giving her blonde hair instead, though some manga art make it a greenish yellow. Interestingly, the "color-coordinated" jokes went to Fuu and her sorta love interest Ferio, who has green hair and yellow eyes.
Bulma and her daughter Bra from Dragon Ball Z. Her son Trunks retains his purple hair.
Daisuke (red hair and eyes), Dark (purple), Satoshi (blue), and Krad (yellow).
The Harada twins both have brown hair and brown eyes. In the anime, this was interesting because Riku's hair was changed to red instead of brown, but her eye color remained the same, implying that she might have dyed her hair in order to look different from her sister.
A lot of characters have this problem. Rima, Ikuto, Ran, Miki, Dia, Yaya, Nikaidou, Kusu Kusu...
It seems most guardian characters are like this, with the exception of Pepe, who has blue eyes, Suu, whose hair is blonde while her eyes and outfit are green, Il, who has red, and El...whose eyes are always closed.
Most characters from Seto no Hanayome have this eyes/hair match. Sun has gold and Luna has pink (but it's opposite for their mermaid tails - Sun has pink and Luna has yellow). Mawari has a violet combination. Shiranui and Class President have light green eyes and hair. Other characters have more natural combinations of hair and eyes (black or brown).
Very common in Baccano!, as demonstrated by Rachel, Nice, Nicholas, Luck, Ronnie (yellow), Claire, Ennis (reddish-brown), Czeslaw, Dallas, Jaccuzi (brown), and Sylvie (gray). Even more so in the books, where color illustrations apply this to Firo, Isaac, Lua, and Eve as well (not to mention the not yet animated characters).
Most of the characters in Hidamari Sketch have matching hair and eye colors. There's the four main characters (brown, yellow, blue, and pink), Yoshinoya (green), the landlady (brown), Chika (light purple), Natsume (blue-green), Nori (blue gray). In fact, the only character who doesn't is the Principal, and that's only because you never see his eyes.
Though Death Note is very good about natural eye and hair colours - all the Japanese characters have brown or black eyes. Misa wears tinted lenses - her eyes change between brown and blue. Light's hair is probably bleached.
The shinigami Watari (golden-blond hair and amber eyes) and the villain Dr. Muraki (silvery-gray eyes and silvery-white hair) in Yami No Matsuei.
Special mention goes to Kyou Kara Maou for making this a plot point. Shibuya Yuuri's looks (including his black/dark brown hair and eyes) are considered average in his native Japan, but when he ends up in a demon country in another world where the combination is extremely rare, he is hailed as a 'soukoku' (double black) and considered highly attractive and regal looking as a result.
Midori from Midori no Hibi, also notable as the only character in the series (besides her mom) to have naturally unnatural hair color.
Lawrence from Spice and Wolf has gray eyes with gray hair - even though he's only 25.
As depicted on the manga covers of Liar Game, Nao Kanzaki and Shinichi Akiyama have (respectively) orange and yellow hair and eyes.
All of the named girls in Puella Magi Madoka Magica; Madoka (pink), Sayaka (blue), Mami (blonde hair and gold eyes), Kyouko (red), Hitomi (green)...except Homura, who has black hair despite being associated with purple (though it's possible that purple is used because black or grey eyes wouldn't look right, and a Soul Gem being gray or black means something else entirely).
The same occurs with the main cast of Vividred Operation. Even the girls' names invoke their colors.
Wandering Son characters are made to fit this lately. As all characters are either brunettes or raven, the characters all have brown or black eyes. Originally, this trope was subverted, as everyone had Brown Eyes. The mangaka makes sure to make the eyes have the same shade as the hair, too.
Ai no Kusabi has Riki with black hair to go with his black eyes, which is significant to the plot.
Ririchiyo (purple), Karuta (pink) and Zange (red) of Inu X Boku SS.
Science Ninja Team Gatchaman has Jun, who has not only green eyes but green hair as well. Averted in the OVA version, however (though they had initially considering making both her hair and eyes blue).
Nanami Momozono from Kamisama Kiss has brown hair and brown eyes.
Many of the girls from Hagure Yūsha no Estetica have this. Chikage Izumi and Minami Aihara both have brown hair and eyes. Haruka Nagase has green hair and eyes. Princess Listy his yellow hair and eyes.
Kagerou Project: Shintaro, Hiyori and Haruka have black hair and black eyes, Ayano has large brown eyes that match her hair (anime only; other adaptations have her hair a much darker shade), Momo has strawberry-blonde hair and similarly coloured gold eyes (the anime gives her black eyes instead), Kano has light blonde hair and yellow eyes, Ene has medium blue-turquoise hair and eyes of the same shade and Hibiya's hair and eyes are the same shade of pale brown.
Polaris and Psylocke both have unusual hair colors (Psylocke's is purple, Polaris' green), and their eyes match. The New X-men's Surge has blue hair and eyes.
Of course, Psylocke started out as a blonde who dyed her hair purple, then got (against her will) bionic eyes to match (after losing her original blue eyes), then got body-swapped into a Japanese body and dyed her black hair purple.
Ditto for Surge: when asked, she confessed her blue hair "came from a bottle".
Polaris is all natural, though (when we first met her, her hair was dyed brown. Green is its natural color.)
Melisandre, from A Song of Ice and Fire, has red hair and eyes. She also always dresses in red and worships a god associated with the colour red as well. Averted with just about everyone else, though, with the exception of 'Young Griff', whose eyes are a curious shade of blue to match his dyed blue hair. He's actually Aegon Targaryen (supposedly), and it's a clever disguise, hiding both his distinctive Targaryen hair (silver) and eyes (purple, but reflect the blue from his hair).
"Bess, the landlord's daughter", the love interest of the titular bandit in the poem "The Highwayman", has black hair and black eyes.
Ilse Burnley from L.M. Montgomery's Emily of New Moon has yellow hair and yellow (actually technically very, very light brown—"almost amber") eyes.
Doc Savage has bronze-flecked eyes to match his bronze-flecked hair and skin - hence the "Man of Bronze" moniker.
Keele Zeibel in Tales of Eternia is a double example of sorts; his hair colour is either blue or purple depending upon the picture you are looking at (and has varied widely in shade and intensity of said blue or purple, besides...), with his eyes always being blue or purple to match.
Due to hardware limitations, everyone whose pupils aren't completely black/a dark dot in the first three games. There are a few exceptions however.
Ema Skye, who, throughout the games, both averts and plays straight this trope, with her amazing color-changing eyes, which are of a bright blue color in the first game (she has brown hair), but seem to be of a rather brown-ish color in her small profile picture in Apollo Justice and during her appearance in Ace Attorney Investigations.
Persona 4: In the original game, there were only 2 characters who's hair didn't match their eye color. Teddie's human form (Blond hair, blue eyes) and Izanami's human form (whitish-grey hair and RED EYES), both of who are otherworldly beings of some sort.Kanji, meanwhile, had blond hair and black eyes, but that's because he bleaches his hair.
The anime added Aika Nakamura, a blue-haired girl with dark brown eyes who has the uncanny ability to deliver fresh food to the team no matter where they are (even when they're being chased by a local delinquent), remaining darn near emotionless the entire time.
Most of the main characters are subject to this trope—the only notable exceptions are Rose (black hair/green eyes), Ledah (blond/red eyes), and Malice (blond/blue eyes). And maybe Cierra, whose eyes are reddish purple.
From the same series, we also have Maria and Meria, the heroines of Knights in the Nightmare. Their antagonist counterparts, Marietta and Melissa, are no different.
To make matters worse, a few gym leaders' eye have been recolored to match their hair color. Yes, I'm talking about Whitney◊ and Falkner◊ (and Jasmine◊).
Game Freak has been doing this with most of their characters lately. It's very apparent with the protagonists, where only Brendan◊ and May◊ have different colored hair/eyes.
Wally IS this trope. And not just his hair and eyes, his pants and even his Pokémon (manga-wise) are all green. And in the Adventures manga, he had to wake up Rayquaza. Needless to say, it's green◊.
Averted with Hilda and Rosa in Generation V, who have brown hair and blue eyes. Played straight with Hilbert and Nate in the same generation. Generation VI averted it with both protagonists. Both of them have blue eyes, but neither have blue hair. The male character has brown hair and the female character has blonde.
The whole party except for Mizuti in the first Baten Kaitos game seems to have this. Kalas with blue hair and eyes, Xelha with blonde hair and yellow eyes, Lyude with red hair and red eyes, and, finally, Savyna with dark purple hair and dark purple eyes.
And, by extension, the whole Classic Kirameki Saga, with only two exceptions: Patricia McGrath in Tokimeki Memorial Pocket on GBC (who, as a foreign student, gets the Phenotype Stereotype treatment), and Megumi Juuichiya in the Motto! Tokimeki Memorial Radio Drama stories (who's a rare case of Cute and Psycho in the series).
Its spinoff series, Rune Factory, has a couple as well. The first has Bianca with purple hair and eyes, Tabatha with light blue hair and eyes, and Mei with dark brown hair and eyes. The second has Mana with black hair and eyes. The third has Monica with orange hair and eyes, Pia with pink hair and eyes, Sofia with purple hair and eyes, and Evelyn with fuchsia hair and eyes. The fourth features (possible) protagonist Frey with green hair and eyes, as well as Leon with light blue hair and eyes, Dolce with pink hair and eyes, Xiao Pai with mousy grey hair and eyes, and Bado with blue hair and eyes.
Kira from Infinite Space has mint-green eyes and hair. In the artbook, the Schneizer brothers' eyes have the same color as their hair (Bastian has dark brown and Dietrich has silver), but in the game, their eye colors are closer to gold.
In Golden Sun: Dark Dawn this continues: Rief and his sister Nowell are of the Mercury Clan and have blue eyes and hair, Amiti has blue eyes and hair, one of many hints at his ancestry, and during the final sequences of the game, Matthew's normally blue eyes become gold eyes.
Tali from Mass Effect is a rather more literal example than most, both her visor and hood being purple in color.
In Roommates, Rakesh has dark grey hair and eyes. Anne's eyes and hair are both brown, but they're different shades, with her eyes being darker and her hair a lighter coppery tone.
The Inklings of Splatoon have irises that match the color of their hair, which in turn matches the color of the paint their team must spread. Oddly enough, the eyes don't match when they're in squid form — they instead have black irises.
Seems to be a characteristic of every character in Sea Princesses, even the ones with blue eyes or pink hair.
All fairies in The Fairly Oddparents have the same eye colour as their hair colour. This is especially noticeable in the episode where Cosmo and Wanda end up taking each other apart with voodoo dolls, then putting themselves back together. One failed attempt had Cosmo and Wanda end up with each other's hair, creating a contrast between Cosmo's green eyes and pink hair, which belonged to Wanda, and vice versa.
Spike as well, for particularly scaly definitions of "curtains".
A few other background ponies get this treatment as well.
Starting with season 2, several unicorns get this treatment in a different way. The auras seen when they use magic will often match their eye color.
In My Little Pony And Friends, there's Buttons (who has blue hair and blue eyes, but has a red streak in her hair as well), Wind Whistler (Pink hair and eyes), Galaxy (her eyes were pink, and her hair was pink, red, and white), Gingerbread (who had blue eyes and blue, purple, and pink hair), Masquerade, Sweet Stuff (Purple eyes with purple, white, and pink hair), Fizzy (Pink eyes with pink, green, and white hair), Rosedust (Pink hair and eyes), Honeysuckles (Pink hair and eyes, though her eyes are blue for the toy), Lily (Purple hair and eyes), Baby Half Note (Turquoise hair and eyes), and Baby Sleepy Pie (Blue hair and eyes).