1. Discover your natural shade.
Find a mirror at the drugstore and put the box's "natural" swatch next to your roots. Once you've found your natural hue, you'll know what you can realistically expect from each dye. (PS Your natural colour is not the colour of your current dye job.)

Deepening your shade from medium reddish-brown to a deep chocolate, à la Julia Roberts, is a realistic colour change. Photography by Dan McMedan/Getty Images (left) and Keystone Press

3. Choose a tone.
Most boxed hair dyes are categorized by tone: W or G for Warm or Gold; N for Neutral; and C or A for Cool or Ash. If you have warm golden skin, you'll need a warm hair colour. If you have a cool pinkish complexion, you'll need a cool colour. Look at the skin on your inner arm to decipher whether you have golden or pink undertones.


Whether she's blond or brunette, Sofia Vergara chooses warm caramel tones to complement her golden complexion; Photography by Keystone Press (left) and Steve Granitz/Getty Images

This story first appeared in the July 2015 issue of Canadian Living magazine.