How she missed: Too much processing (coloring, straightening, perming) fries hair; Karen's blonde ends were frizzy and dead. And faded color can blend with skin tone, dulling the complexion.
It's a hit! Frédéric trimmed all dead ends and added layers to increase volume and give Karen's cut some shape. Then he gave her a hazelnut base color to warm up her skin tone before adding caramel highlights ("I want to give her lightness without making her blonde, which isn't right for her because of the yellow in her skin," Frédéric said). A golden brown gloss toned down any remaining brassiness and boosted shine.
The point: Hair has to be in good condition for color to look natural and fresh. Don't overprocess.