'The paler the skin tone, the lighter you can go. The richer the skin tone, the more depth you need to add,' explains of her simple trick used to identify how to choose a hair hue to suit you.
The New York native boasts her own salon and product line, plus the role of Beyonce's hair colourist. No biggie.
When it comes to her famous client's coveted colour (that's 'honey' when you think of the singer's signature style, but 'baby blonde' when she wears it lighter), Hazan says 'different variations, depending on your skin tone' will work on most of us.
Should 'Beyonce-blonde' tempt you, Hazan recommends bringing inspiration to the conversation with your colourist by way of images, 'but bare it in mind that all pictures are filtered.' Especially Instagram and Pinterest shots, of course.
Hazan's speciality is taking dark hair light, all while keeping it healthy, which is no mean feat. 'It's hard to make dark hair blonde without it turning brassy,' the colourist explains. 'If you're thinking of going blonde I suggest taking it slow. It's hard on the hair and can be damaging to dye someone's hair from dark brown to platinum blonde in one session. It's best to make multiple appointments and lighten your locks little by little each time.'
In this case, don't even think about hitting the bottle at home. 'If you are wanting to cover grey or make your hair darker at home, go for it,' she says. 'If you want to lighten your hair or get highlights, definitely go to the salon.'
Regardless of whether you're going blonde or not, Hazan also says it's also a good idea to have your hair cut the same day as your colour change. 'Sometimes new colour needs a new style,' she reveals.
The best way to preserve colour, according to Hazan, is by arming yourself with products specifically meant for colour treated hair. 'Use products that are 'colour safe', paraben- and sulfate-free, have UV protection, and that say 'hydrating', 'cleansing' and 'moisturising'. Right after your colour appointment you have to use products that can replace the proteins and hydration you just lost.'
She adds that a conditioning mask (try her , £34) 'will help to add moisture back into hair' and that you must use a heat protector before the use of styling tools. 'The product will act as a buffer between the heat and your hair,' she explains, ergo minimising damage.
While we might not live in sunny LA like Bey,Hazan says it's also very important to protect your hair from the heat and sun. 'Always use products that have UVA and heat protection,' she instructs. 'My new has been specifically made for that very purpose.' The invisible mist protects from premature colour fading by blocking out humidity and UV rays. Add it to the list of important things you never knew you needed.