Billie Lourd had a colorful pool party ahead of turning 25 on Monday. The Scream Queens star and her guests celebrated her birthday with a rainbow-themed party that included a water slide and a photo booth that didn't go unused. Teen Wolf's Colton Haynes was among Lourd's friends at the bash and posted a fun pic to Instagram from the soiree, along with a sweet message. "Too much fun celebrating @praisethelourd 's b-day," he wrote. "Rainbows, water slides and food trucks...the best :) Happy b-day boo!!!" Lourd also shared some fun photos from the party, as well as a throwback image of herself at Disneyland with her mom, Carrie Fisher, and grandmother, Debbie Reynolds, who both died at the end of December.