James Cameron's Avatar captivated audiences when it hit theaters in 2009. The nearly three-hour sci-fi epic takes viewers on a journey to the lush, habitable moon Pandora, inhabited by the indigenous Na'vi people.

Growing up to 12 feet tall with blue skin and yellow eyes, the Na'vi are foreign, but they're also undeniably human—an intentional choice on Cameron's part, subliminally urging viewers to side with the Na'vi when humans begin to invade Pandora to exploit its natural resources. The director talked with Empire Magazine to explain how this motivation helped drive the character designs for the Na'vi.

"I wanted the audience to side with the Indigenous people and see the humans as the invaders from space who were ravaging their world. A flip on all the 'aliens invade Earth' stories we grew up with. I was betting that through the power of cinema the audience could be taken on a journey in which they became the enemy, and maybe as a result saw themselves, however briefly, as nature sees us. Alien. Invader. Destroyer. The design of the Na'vi was the result of an intensive design process with some really talented creature and character artists. Some of the early designs came out too amphibious or lizard-like. I wanted relatability. I figured we can relate to dogs and cats emotionally, so we gave the Na'vi expressive tails and ears that had that familiarity, and in the end, their most alien features were their scale and their color."

While it's hard to imagine the iconic Na'vi being any color, Cameron says that making them blue wasn't exactly cut and dry—it was a process of elimination.

"As for the color: green was taken. There was a long history of green aliens. Plus, the Hulk. And the human colours, pinks and browns, weren't alien. Spongebob was yellow. That pretty much left blue and purple."

Though the director says that purple is his favorite color, that seemed more suited toward the brilliant bioluminescence on Pandora, so blue it was.

Related: James Cameron Says Avatar Came to Him in a Dream, and His Drawings Stopped 'Tinfoil Freaks' Suing Him

Cameron Shares Scrapped Character Design Concepts for Na'vi: 'It Would Mess with the Rating'

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20th Century Studios

Once the color was settled, Cameron had a few other character design changes to work out until the final Na'vi design was complete—including a concept that his mother saw in a dream that would have radically changed the film.

"Also, my mom told me about this dream she had where there was a ten-foot-tall blue woman with six breasts. Cool image. I drew her, but the six breasts thing didn't come out looking as good as it sounds, plus it would mess with the rating. So, anyway...blue."

Avatar's long-awaited sequel, Avatar: The Way of Water hits theaters December 16.