01/09/2012 at 06:00 AM EST
and Jay-Z's baby girl
Blue Ivy Carter arrived Saturday
, and while little girls are customarily pretty in pink, this baby is also being surrounded by touches of blue.
This was the case over the holidays, when, in anticipation of the baby's birth, the parents-to-be sent pals blue Christmas gifts, a source tells PEOPLE.
Sources and fans suggest the couple chose the name "Ivy" because of the number 4 or Roman numeral IV, which is significant in Beyoncé and Jay-Z's relationship.
Beyoncé's birthday is Sept. 4, while Jay-Z's is Dec. 4; the two married
on April 4 in 2008; they reportedly have matching "IV" tattoos on their wedding fingers; and Beyoncé named her latest album 4
And the significance of the baby's first name, Blue? Well, Jay-Z has three albums with the word "blueprint" in their titles: The Blueprint
was released in 2001; The Blueprint 2: The Gift & The Curse
, in 2002; and The Blueprint 3
, in 2009.
In lyrics, Jay-Z has rarely been coy about proclaiming himself the best rapper ever. "I'm the Blueprint, I'm like the map for 'em," he said in "A Star Is Born," from The Blueprint 3.
Fans have also chimed in on the name. "Blueprint was the hottest album ever sold by Jay-Z! their child's name makes a lot of sense!" Tweeted @kisssmyDIAMONDS
And Tweeted @omgitsralph
: "There's a meaning in Ivy Blue. IVy = a roman numeral for 4 which is Beyoncé's favorite number and BLUE for Jay-Z's Blueprint albums. Wow."
Perhaps at some point the parents will make clear why they chose the name.
Until then, there's one thing the family is clear about, as proud aunt Solange declared on Twitter on Sunday. Blue Ivy, she said, is "the most beautiful girl in the world."