Sexy Stars Going Green (Bikinis) ... Happy Earth Day!

It's Earth Day y'all, and these Hollywood hotties are keepin' it green and keepin' it clean in their green bikinis ... Be a force of nature with the ladies who are cleaning up their acts!

Leaf your worries behind with Elsa Hosk, who shined in a metallic green bikini ... and check out the strapless swimwear on Saweetie -- you grow, girl!

And you wont be-leaf how gorgeous Emily Ratajkowski looks in green!