Billie Eilish just shut down the haters who have a problem with her signature neon green hair ... to a TMZ reporter who asked her about the look at the time. "What do you mean mullet?

The star, known for her edgy red carpet ensembles, arrived at the ceremony in a simple black look Billie Eilish and the red ... the singer donned a glimmering green and black Gucci logo suit ...

There is no one cooler than Billie Eilish ... sneakers. No Eilish-inspired look is complete without heavily accessorizing, so I stacked chunky silver jewelry and tied a green thrifted handkerchief ...

"I've literally never done anything in this realm at all," Billie ... you look good, you look good." Addressing the unfair standards women are often held to based on the way they dress, Eilish ...