If the pink is barely noticeable on the outfit, it doesn't count. A significant part of it has to be pink. It could be the skirt or the bodice is almost all pink, or there is a lot of pink trimming on almost every part.
Pink hair and makeup alone don't count (they can be included though).
Jewelry can count, as long as it's obvious that it's pink, without requiring a closeup.
It has to be an actual princess to fit this trope, by birth, marriage, adoption, etc.. This can include fantasies of being a princess (as long as we see the fantasy) or someone playing one in a show, play, or something else. If it's just a woman or girl in a lovely pink dress with no mention of royalty it's the Super Trope of Pink Means Feminine.
Also applies to some of the mechas in Gundam SEED: Cagalli's Strike Rouge is the Strike Gundam colored pink, and Meer's pink ZAKU, called "Zaku Warrior Live Concert Version", though it was only used as a stage prop for one of her concerts, and never pilots it herself.
The standard female outfit of the Earth Federation in the original Mobile Suit Gundam is pink. One of the girls wearing said outfit, Sayla Mass, happens to be a princess(Sorta, considering the Zabi family userping Zeon and everything.
Princess Allura/Fala from Voltron/Go Lion, whether it's her grand dress, jumpsuit, swim suit, or pilot uniform. She wears blue in the sequels, however, to match her Lion.
In Slayers, Princess Amelia's most often-worn dress for diplomatic duties is a frilly pink one, and she's seen wearing it in several episodes of the anime and in supplementary materials. Her regular traveling outfit also has pink touches on it.
Rare Eastern-stylized example: Konoka from Mahou Sensei Negima! during her princess moments often wears a pink kimono.
Chibi-Usa in Sailor Moon wears a pink sailor senshi costume and has pink hair. As the daughter of the future queen, she's by definition a princess. Her princess dress in the anime is white and identical to her mother's, but the manga has her break away from her mother and fall into this trope, with a pink cherry-blossom-evoking dress instead.
It's generally assumed that while Usagi's image is associated with silver and white, all of her powers result in huge pink blasts of light (if they aren't moon-shaped or rainbows), including her transformation sequences up until Eternal — she's pink on the inside.
Nia Teppelin from Tengen Toppa Gurren Lagann starts wearing a pink, princess-y dress with golden shoulder armor, then goes on to have a pink hoodie, and a pink, one piece dress after the timeskip.
May Chang from Fullmetal Alchemist is a a Xingese princess and wear a mainly pink outfit.
Kyou Kara Maou: Wolfram, 'nuff said. That pink, frilly nightgown seems to be a major favorite of his.
In Digimon Adventure, Mimi wears a pink dress when she is posing as a princess for a Gekomon kingdom.
And so does Palmon!
Cornelia and Euphemia in Code Geass both tend to wear pink.
It helps that they both have hair in different shades of pink.
Don't forget Nunnally, who also has a (very) pink dress.
Even though she doesn't live as one, C-ko is an alien princess who wears pink often.
Princess Millhiore F. Biscotti of Dog Days, so much she should provide the page picture. Her hair is pink. Her eyes are pink. Her ears and tail are pink. Naturally, her dress is pink. She's more pink than color pink itself.
Board Games
Aside from the Disney-branded versions, most versions of Pretty Pretty Princess show a princess wearing pink. And yes, the Sleeping Beauty version shows the pink dress.
Sleeping Beauty: Aurora's dress ends up in some color war in the movie, but in The Merch for the Disney Princesses, it's usually pink. It's likely to distinguish her from Cinderella, another blonde with a blue iconic dress. (Cinderella's dress in the movie is white and silver, but blue worked better for the colour-coding). Many of the older fans prefer the blue it is for the majority of the movie. Occasionally it is colored purple in The Merch, but that's unlikely to happen anymore with Rapunzel prancing around with a purple dress and long, blonde hair.
Maid Marian, in the animated Robin Hood, wears pink. She's not technically identified as a princess, but in this version she is stated to be the King's niece, so it's more or less implied.
After Buttercup becomes The Princess Bride, she is seen wearing five different dresses, one of which is full-on pink; another is a sort of peachy-pink.
Live Action TV
In Disney's Princess Protection Program, the Princess requests a pink silk nightgown, and a pink gown she wears at one point is actually a plot-point.
Ahim de Famille in Kaizoku Sentai Gokaiger takes this a step further; she's a former princess who serves as this season's Pink Ranger.
Barbie is largely an aversion to this when it comes to the dolls. Despite all the pink associated with her normally, when there is a princess doll, even if it's labeled as some kind of princess, her clothes are rarely pink. The films are a different matter though.
While not officially a Princess (though she might as well be; she rules her country by birthright and.. um... hair right... and doesn't seem to have parents), Lady Lovely Locks is just about the most frilly pink girls' toy there was in the 80s. It was, in fact, her signature color, with her two handmaidens generally being characterized with blue and yellow, and the antagonist of her various stories, Duchess Ravenwaves, with purple.
Zelda wears a pink dress in Zelda II The Adventure Of Link, something which is made more clear in the instruction booklet than the game itself. Judging by some of the promo art from the original, her dress there may have also been pink, although its in-game color is whatever color Link is wearing. In The Legend of Zelda: Ocarina of Time her dress was mostly pink, and subsequent games in the series usually have her wear a gown with pink accents.
Zelda wears blue in the original release of The Legend of Zelda: A Link to the Past, as shown in the manual and promo art; the actual in-game sprite appears dressed in more of an off-white. However, her updated pink dress in the GBA remake is an exact copy of what she wore in the Japanese box art of the original SNES release. Just compare◊ them◊.
In The Legend of Zelda: Skyward Sword, this is played with : Zelda is a regular citizen who wears pink, but she dons a white dress and brown, high sandals when you meet her again after The Reveal.
For bonus points, Super Smash Bros features both Peach and Zelda in their pink dresses (even if the latter has it as an alternate costume in Brawl).
Played with with Remilia Scarlet in Touhou; 1. She's not a princess, however, there are several noble or royalty motifs to her (her theme is called "Septette For The Dead Princess/Queen", she is called "The Queen/Empress Of The Night", she owns a mansion that is Bigger on the Inside, has hundreds if not thousands of Fairy servants, often displays a remarkable, charismatic facade whenever she's not being a Bratty Half-Pint in personality, and 2. Her dresses used to be white. They became pink after she spilled enough blood on her dresses to stain them too much for them to ever become white again. This is because she has, surprisingly for such a powerful vampire, little appetite for blood and is also a messy eater. However, this quirk is responsible for spawning her other, most widespread of her titles: The Scarlet Devil.
Alyssa from Gungnir, otherwise known as Princess Alessandra Dlacroa, dresses mostly in pink and red and wields a giant lance covered in big pink roses.
One of the unlockable characters in Rayman Origins is a Teensy Princess. Not only is her dress pink, but her crown is pink as well!
Web Comics
Last Res0rt's HRH Adharia doesn't just prefer pink, Adharia IS pink — well, all the fur except her mane is, anyway.
Her preferred color in clothing actually seems to be purple/lavender. Of course, given her fur, this may just be a way of avoiding pink overload.
The aptly-named Princess from Castleveina RPG has a pink dress as her standard adventuring gear. This is lampshaded later in the comic when in a side panel she meets Princess Zelda (disguised as Sheik) and learns to transform into her other outfit (a green comando-esque outfit dubbed "Metal Gear Princess" by the creator) and back.
Princess: I have this great pink dress... Sheik: Of course you do. It comes with the territory.
Firmly averted in The Fourth. Lord Skärva has set up a room in his castle for Princess Veronika since he kidnaps her quite a bit. Her reaction to being locked in it is "Ugh. So much pink."
Aelita of Western Animation Code Lyoko is often argued to be the "princess" of Lyoko, to the extent of it being her official nickname. And she does have quite a thing for pink. To the point of having a pink cell phone and a pink laptop. Oh, and pink hair.
Princess Peregrine of the Storm Hawks episode "Royal Twist".
Zelda, on the Animated Adaptation of The Legend Of Zelda, normally averts this trope, as her day-to-day garments are mostly blue and brown; however, in the water park episode, she wears a pink bathing suit. Spryte, the Fairy Companion who is also a princess, plays the trope ramrod straight and wears pink all the time.
Piggy, on Muppet Babies, lives and breathes this trope. Not only is her everyday outfit pink (as is she, being a pig), but whenever she plays "Princess Piggy" as part of the babies' big imagination project of the episode, she's decked out in full pink Princess Classic costume. (The only princessy exception was the Star Wars spoof, in which she was dressed like Princess Leia).
Princess Celestia in My Little Pony: Friendship Is Magic is a very light shade of pink, closer to white. More prominent in her toy versions. Averted by Princess Luna, whose colour-scheme consists of blues and purples, and played straight by Princess Cadance (introduced in the Season 2 finale), whose body and part of her mane are both pink.
While Princess Allura in the original Voltron played this trope straight, in the 2011 sequel Voltron Force she averts it - both her civilian wardrobe and Voltron Force uniform are colored primarily in shades of blue, the color of her Lion. She did wear a pink outfit one episode.
In a 90s X-Men episode, Jubilee is telling a Fairy Tale with many of the characters in the show, including Scott as a prince and Jean as his princess, and she did wear some pink (but mostly purple).
