Leighton Meester: Blonde to Brunette

"When darkening your hair, stay within one to two shades of your natural hair color," Chuck says. "If you're going from blonde to dark brown, you're going about eight shades darker and that's not something we recommend at home because that's actually a professional color treatment."

And if you think semi-permanent color will work as a temporary brunette fix, think again: "Semi-permanent hair color washes out in 6 to 12 shampoos, but only on natural hair," Chuck says. "You can't use semi-permanent color on blonde hair to go dark brown because it will stain. The majority of it will wash out, but you'll get residue, staining, and possible discoloration."

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