Kylie Jenner apparently missed the memo.
The 18-year old reality star joined half-sisters Kourtney, Kim and Khloe Kardashian (along with mother Kris Jenner) at a party to help Cosmopolitan celebrate its 50th anniversary on Monday night.
(The magazine controversially put these people on its milestone cover and labeled them America's First Family.)
But Kylie was the only member of the group not to dress in black, going in the complete opposite direction on the color spectrum.
"I didn't get the 'wear all black' email," Jenner joked on Instagram.
Check out photos from the red carpet event below and decide: Who dressed best?
Kylie Goes Rogue
Someone forgot to give Kylie Jenner the memo in this photo. It's an all-black affair!
First Family Photo
Khloe Kardashian, Kourtney Kardashian, Kim Kardashian, Kris Jenner and Kylie Jenner gather here on the red carpet. They are on hand to help Cosmo celebrate its 50th anniversary.
Kris Jenner, Kourtney and Kim
Kris Jenner helps Cosmo celebrate 50 years as a magazine by posing here with Kim Kardashian and Kourtney Kardashian.
Kim Kardashian for Cosmo
Kim Kardashian is getting close! She's almost a second-time mother! The pregnant star flashes her figure here at the Cosmo 50th birthday part.
Kris, Kim, Kourtney
Kris Jenner is smiling in this family photo, but Kourtney and Kim did not get the memo. They have their game faces on.
Sisters in Black
Sister unite! Kourtney and Kim Kardashian both went black for the 50th anniversary Cosmo party in Los Angeles.