The 19-year-old star has refreshed her look and shown off her fresh style with a social media selfie as she returns to her dark roots.
Sharing a snap on Instagram, she simply wrote: "Miss me?"
The new 'do has gone down well with her followers, including Claudia Sulewski - who is dating her brother Finneas - as she commented: "Insane."
Plenty of her fans have responded with heart eye emojis and red hearts, and others shared one word replies with one follower writing: "Yes."
Another added: "JESUS CHRST (sic)"
Meanwhile, the 'Bad Guy' hitmaker recently revealed how her appearance has an influence on her confidence, as she ditched her jet black hair with neon green tips because she felt too recognisable in public.
She told Vanity Fair magazine: "My attitude used to be like, ‘I can't go out, I can't go here, I can't go there'.
"I wasn't able to go to a park or go get coffee, It freaked me out. But in the last year I opened up to it."
As well as her hair, Billie also stood out because of her outfits, as she took time to adjust to being able to blend in.
She explained: "I was like, ‘I only want to be seen if I look like myself.' So I would never wear anything normal."
She ditched the bold colours earlier this year, and hairstylist Lissa Renn previously opened up on the six-week process.
She said: "The process is real when you're doing it right. 6 weeks to get all the black out of her ends without damaging it, along with her following my strict haircare regime.
"We actually loved all the stages of lifting color but the end result is [fire emoji]."