Rainbow-Themed Pool Party. Make a splash for your 40th birthday with a fun pool party! A rainbow theme will inject vibrant colors and even more lively energy into the celebration.

It’s your blowout 40th birthday party! Just make sure it’s casual enough that guests won’t be caught off-guard by attire, and be sure they have a safe way to get home afterwards. 41.

Khloé Kardashian just threw a huge, fun, Wild West party for her 40th so if you have a big birthday coming up, here's how you can celebrate like a star ...