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 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.
It's generally assumed that while Usagi's image is associated with silver and white, all of her powers in the first anime 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.
Chibi-Usa in 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 first 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.
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.
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.
Most of the princesses and other leading ladies in Grimm's Fairy Tale Classics have at least some pink in their outfits. It's easier to list the exceptions: Snow White from "Snow White and Rose Red" (in her case it's because Rose Red is already wearing pink), Lisbeth from "The Magic Heart", and the princess from "The Iron Stove", who all wear green, and Allerleirauh from "The Coat of Many Colours", who has purple, yellow, blue, white, and red dresses, but not pink.
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 pinker than the color pink itself.
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. This is most 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.
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, 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.
Princess Celestia in the current My Little Pony line is usually pink, although her character in the TV show is clearly white (albeit with a pale pink outline). This is apparently because Hasbro thinks girls will only buy the toy if it's pink. The fandom was less than pleased, and it wasn't until a few years later that a white Celestia toy was released. Naturally, right around the same time, Princess Cadance, who is pink in the show, was introduced, so the toyline still has a pink princess.
In The Legend of Zelda: Skyward Sword, this is played with: At first, Zelda is a regular citizen who just happens to wear pink, but she dons a white dress and brown, high-laced sandals when Link meets her again after The Reveal.
For bonus points, Super Smash Bros. features both Peach and Zelda in their pink dresses (although the latter has it as an alternate costume in Brawl).
The 16th main installment of the beatmania IIDX series is subtitled "Empress." It has a very, very pink user interface.j
Even in Persona 4, Yukiko's shadow is a pink-wearing princess.
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, best known title: 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!
Princess Sophia wears a dark pink gown, with black accents and (later) a white cape, all throughout the Awakening series.
In Final Fantasy V, Krile's job class outfits tend to feature this color more prominently than the others (even Princess Classic Lenna). Her knight's armor is completely pink.
Last Res0rt's HRH Adharia doesn't just prefer pink, she 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 commando-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.
Aelita of 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, in 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 first episode, she's seen wearing a pink nightgown. 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. Though Twilight Sparkle is mostly purple, she has magenta magic and wears a coral pink dress upon her coronation.