Hilary Duff Explained Why She Dyed Hair Green

— -- What in the world would make Hilary Duff dye her blonde tresses green?

Turns out, she had a personal reason for changing things up.

"I've never done anything like this, and I was just in Cabo [San Lucas, Mexico] with my son and I was staring at the ocean and I was like, 'I want that on my head,'" she said during her twelfth appearance on The Ellen DeGeneres Show today. "So this happened."

Duff, 27, who is set to star in TV Land's new comedy "Younger," added that one person in particular was very curious about her new 'do: her son, Luca. Luckily, the three-year-old, whose father is Duff's ex-husband, former NHL player Mike Comrie, loves the new look.

"Here's the thing: Luca is very particular about how he likes my hair. There are absolutely no buns on my head, no ponytails. I'll have a ponytail and he's like, 'Um, hair down, Mom. Hair down, please,'" she explained. "Now he likes to go through his roster of colors that he knows. He's like, 'Your hair's purple,' and I'm like, 'No, it's green.' He's like, 'Nah.' I'm like, 'Yeah.' He's like, 'It's blue.' 'No.' 'It's purple.' 'No.'"

"He's very, very funny," Duff added, smiling.