Gabe Ugliano once told Percy's mother, Sally Jackson, that there was no such thing as blue food or drink. From that point on, she went out of her way to make blue foods to prove Gabe wrong. She had a rebellious streak like himself, Percy recalled. Mrs. Jackson would always bake blue cookies and buy blue candy for Percy, or would make a blue cake on his birthday. Percy's favorite color is also blue. This could be because his father's domain is the sea, therefore blue, or simply because his mother likes to make blue foods. Either is considerable.
Sally always made blue food for Percy. When Percy came home from Yancy Academy, his mom brought blue candy from the sweet shop, Sweet on America. To Percy, nectar tastes like his mom's homemade blue chocolate chip cookies. Also, when he first had dinner at Camp Half-Blood, he asked for "Blue Cherry Coke" to appear as his drink.
After Percy woke up, Sally Jackson decided to create a Blue Cake, along with some other delicious Blue food. Later, when he finishes eating, Percy brings up the idea to spend his summer at Camp Half Blood. Sally quickly says no, which makes Percy curious.
Percy promises his mother that if he survives, he would give his mother some sort of sign, "something blue." After Kronos is defeated, he asks Zeus to light up the top of the Empire State Building blue to let his mom know that he is safe. Without any argument, Zeus snaps his fingers and grants Percy's request.
Later, Annabeth Chase brings Percy a birthday cupcake with blue frosting which, according to Percy, looks "like a brick with extra blue cement", when Annabeth told him that Tyson helped her bake the cake.
When Percy is at Camp Jupiter eating dinner his first night, one of the aurae gave Percy a blue drink with his dinner. Hazel Levesque didn't understand the meaning of the blue soda, but it seemed to make Percy happy.
While at the dinner table, Piper McLean notices that Percy is eating an all-blue pie which includes the whipped cream and filling.
On the Argo II, Percy has blue nachos.
Magnus Chase mentions multiple times that he hates the color blue.
- Blue is one of the primary colors and on the visual spectrum, between green and violet.
- Percy Jackson simply adores this color, while Magnus Chase, in contrast, simply despises it.
- Percy reveals that he wears plain blue boxers.