The longer your hair, the more weathered the ends are. By adding pigment (instead of bleaching it out), a single process smooths damaged cuticles so hair seems shinier and healthier. But steer clear of burgundy, says Hintermeier. "Bluish-red hair doesn't exist in nature—try gold undertones instead."
Sixty-four percent of Canadians prefer dark hair, according to the Dove study. However, if your real hair color is a distant memory, Hintermeier suggests using your skin tone as a guide: "The deeper your complexion, the darker you can go. Whether you want something natural or dramatic, highlights aren't the only option anymore."
According to a recent Dove Global Hair Study, more than half of American women believe blonde is more beautiful. But liquid alchemy is high maintenance. Hintermeier suggests an allover sandy-beige tone to blend in old highlights and breathe new life into washed-out shades: "You can't always highlight, because you'll end up with white hair."
Highlight junkies afraid of losing their sun-kissed sparkle shouldn't worry. "Your hair always has different shades because the sun naturally makes it lighter on top. Single-process color looks darker or lighter depending on the tone underneath, so you'll keep a nice shadowing," assures Hintermeier.