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.
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.
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.
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.
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.
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!
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.
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).
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.