Fun fact: Today is Marilyn Monroe's birthday. And while the occasion could lend itself to a slideshow of our favorite platinum blondes throughout history, we don't really need to look beyond the last few months for some rad examples. Why? It's spring's biggest hair-color trend...again!Hollywood's love affair with the icy-blond bleach-and-tone started in the good old days — from Jean Harlow in the '30s and Monroe in the '50s, to Madonna in the '80s, Gwen Stefani in the '90s, and Rita Ora today. And we've been tracking the trend's resurgence , which has been brewing in L.A. all spring.The raven-haired Rooney Mara was perhaps the most unexpected adopter. "It’s a big deal!" her colorist Cassondra Kaeding tells us, adding that it's not a decision she encourages her clients to take lightly. "Consider time, maintenance, the condition of your hair, and money. Like any relationship, you've got to make a commitment, because it’s hard on your hair and taxing to reverse." Silk pillowcases and a hair-product overhaul can help maintain the integrity of your strands, she says.