Billie Eilish reveals she's been hiding her blonde hair for months

American singer-songwriter Billie Eilish recently debuted her new highlighted hair and the singer has revealed now that she had been keeping her hair transformation under wraps since mid-January.

According to People magazine, the 19-year-old singer uncovered the mystery about her new hair tone during a casual Instagram Q&A session on Saturday (local time).

The 'Bad Guy' crooner addressed various fan inquiries concerning her new haircut -- including why she had been staying quiet about it for such a long time.

"'Cause it took six weeks to accomplish," the star wrote alongside a photo taken on January 16, after the "first round" of the hair dying process. The image showed Eilish rocking a two-toned look: a platinum blonde on top that faded into a more red-leng hue. Eilish also said that even after all of the work that went into getting her light blonde colour, her hair is "so healthy."

"I wasn't expecting that at all," she explained, adding, "It's actually healthier than it's been in a longgggggg time."

Per People magazine, the pop star's hair specialist recently shed some light on the hair transformation, writing in a since-deleted post that she had been step by step easing up the hitmaker's pure black locks -- leading fans to believe Eilish was wearing a wig when she performed at the Grammys just days before the big reveal.

"The process is real when you are doing it right. 6 months and a half to get all the dark off of her ends without harming it, with her following my strict hair care regime. We really cherished every one of the phases of lifting the hair colour too but the outcome is [fire emoji]," Lissa Renn wrote a month ago and posted a couple of photographs of Eilish throughout the hair transformation process.

At that point, the artist apparently confirmed the fan theories on TikTok,by posting a video that seemed to show her lifting up a dark and green wig.

The seven-time Grammy winner has been exchanging between all-over ink dark and her signature dark with neon green roots, lately. She recently rocked a light greenish-blue tone toward the start of 2019, just as an indigo blue before that.

Eilish made the big reveal shortly after asking fans to guess what colour she would pick next. "did you guess correctly?" she captioned the clip.

( With inputs from ANI )