Crush Blush

There's a blush for won't, and a blush for shan't,
And a blush for having done it;
There's a blush for thought, and a blush for nought,

And a blush for just begun it.

—John Keats

Love—even Puppy Love—makes the young and innocent blush. Whether speaking of the Love Interest, realizing that you are the Love Interest, or actually talking to the person, expect the character to turn red. Very young or innocent characters may evince this even when an attractive member of the opposite sex seems to notice them. Less innocent ones may be driven to it only by the Love Confession.

People prone to the Luminescent Blush or Blush Stickers are bound to suffer these. The Celibate Hero is often but not always prone to it. An apparently hard-bitten character who evinces it is revealing a soft side to himself. Adolescents are particularly prone to revealing they are not as grownup as they pose as.

Contrast Gibberish of Love, which indicates more ineptness than innocence.

Examples of Crush Blush include:

Anime and Manga

Hanaukyo Maid Tai La Verite episode "Forced Entry". When Ikuyo Suzuki teases Ryuuka about her feelings for Taro, Ryuuka blushes furiously while denying it.
Koharu quite frequently in Koharu no Hibi.
It's not explicitly stated in Axis Powers Hetalia, but you look at the way Germany is always blushing around Italy, and tell me you don't see it that way, especially with the overwhelming amount of Ship Tease they get.
Athena and Hinagiku both seem very prone to this.

Comic Books

In Captain Britain, while he recounted some transdimensional adventures, he mentioned a woman. The children listening tease him about how he blushes.

Fan Works

Male examples. Let's just say tomatoes would be insanely jealous of Germany and Japan in Axis Powers Hetalia fanfic Gankona, Unnachgiebig, Unità with how red they become and how often they become red because of Italy.

Literature

In Rick Riordan's The Son Of Neptune, when Ella returns with Tyson, she blushes when she talks to Percy of it. When Percy calls Tyson "you big charmer," Tyson blushes too.
Tales of Kolmar has Lanen, influenced by her father's demon-made attraction charm, fall for him complete with blushing at the very thought of him despite being in her twenties and, she thought, over that kind of reaction to boys. She didn't know he was her father then.
In PG Wodehouse's Jill The Reckless, a Flash Forward recounts how Otis would blush on his wedding.

Video Games

Because it wasn't clear enough that Summon Night: Swordcraft Story's Pratty is gay, she blushs and says "The lovely twin sisters!" upon being told her next opponent was a pair of twin girls.

Visual Novel

Pretty much every somewhat-romantic Visual Novel out there will involve the girl's cheeks reddening around Love Confession time. Just off the top of my head, I know that Katawa Shoujo does this.

Webcomics

In Sinfest, the boy blushes when Baby Blue passes him a note saying he's cute.
In Rusty and Co, Madeline the Paladin blushes when she mentions Derek the Cleric.
In Gunnerkrigg Court:
- Kat when discussing Mr. Eglamore and after embracing Alistair.
- Mort when Antimony thanks him. The significance of the gift may have something to do with that.
In Sandra and Woo, Larisa can induce it in Landon by asking for a lick—and taking it on him, not his ice cream cone.
- Or ask him what her father told him about her.
In Our Little Adventure,
- Rocky gets it when Angelika talks as if he asked for one room for them, and then, more seriously, when he meets up Emily again.
- Angelika when the druid comments on her looks.

Western Animation

Spike blushes after receiving a kiss from his crush Rarity, in the My Little Pony Friendship Is Magic episode "Secret of My Excess".
In the Batman: The Animated Series episode "The Cat and the Claw", Bruce Wayne meets Selina Kyle for the first time and blushes, even stumbling over his words a little speaking to her.