The "Therefore I Am" singer added that at first, she didn't think the new hue would become a reality. "I kind of thought of it as a dream," she shared. "I didn't think it was going to happen 'cause my hair's been through so much. I thought I'd burn it all off if I tried, but I did it!"
She also told the talk-show host that going blonde took about six weeks to complete. "It's very hard," Eilish admitted. "We started in January, Jan. 16 I think was the first day. Then it was two weeks of nothing -- healing, letting my hair take it in and digest and recover. And then again, and then two more weeks. ... Oh my god, it took a long time."
The night before, Eilish was Stephen Colbert's musical guest, where she performed her latest single, "Your Power," off upcoming album Happier Than Ever. While chatting with the comedian, the artist admitted that when she appeared on his late-night show about 10 weeks earlier, she had, indeed, been wearing a wig. Not only that, she dished that one of the first wigs she got was a Billie Eilish costume wig from Amazon. She revealed: "It was awful, it was the ugliest thing I’ve ever seen!"
But, she explained, there was a reason why she needed to hide her locks while the color was in transition. "I looked f---ing crazy underneath," Eilish told Colbert, "and I needed to look not-crazy."
Watch Eilish's interview with DeGeneres below: