In the hierarchy of appearance checklists, color is king. Your sleek new bob isn’t going to do you any favors if your color is brassy, and your finger waves certainly aren’t going to garner any praise if that new chestnut shade falls flat against your skin tone. It's no wonder that there is such an intense bond that develops between colorist and client—particularly in America, where three out of four women color their hair—and Nicola Clarke is exactly that sort of color genius you want to bond with. The color mastermind has built a solid career on her precision for the perfect shade, seen most recently in her transformation of Dua Lipa with the two-tone trend. But perhaps more importantly, she's long sustained the trust of her long time loyal clientele to take risks and change, handling the lustrous locks of some of the most notable Kates (and Cates) around the world, like Moss, Winslet, Beckinsale, and Blanchett, for years. Here, the London-based expert reveals some of the key hair advice that's made her a favorite among notables around the world.

What are some of your personal favorite color moments you've created over the years?
The looks I made for the cover of Lady Gaga's album Born This Way definitely stand out. It was a shoot with the photographer Nick Knight, and I worked on coloring hair pieces a light dusty pink with Sam McKnight, who was styling Gaga's hair. Another great moment was from Madonna's [2000] video for "What It Feels Like for a Girl," which we shot in L.A. I took her much blonder than she'd been in a while at that time.

What would you say is the defining moment of your career so far?  Opening my own salon in partnership with John Frieda. We celebrated with a beautiful launch dinner at the salon with lots of my clients, industry friends, such as Mary Greenwell and Sam McKnight, plus some well-known faces like Kate Winslet and Cate Blanchett whom I've worked with for years. It was a pretty special evening.

What are some of the factors you take into consideration before coloring a new client's hair?
Hair color is super personal and needs to suit the style of the client, as well as their lifestyle. I'll always flag if bigger changes require more maintenance, so they know before they make a decision that's not often always practical. Also, sometimes people might want to add more shades into the color of clothes they wear as their hair changes shade. Makeup will often need a transition from warm and cooler tones, or vice versa.

Where do you think the direction of color-related hair trends is headed this season?
There's definitely a trend toward two-tone hair. It's similar to the transformation the team and I recently did on Dua Lipa—the front strands are lighter/blonder, and the back of the hair is much darker. It's a trend that can be made as extreme or subtle as you want and still have impact.

How often do you encourage your clients to deep condition after getting their color done? Which products do you really believe in to treat over-stressed hair?
I always recommend treatments when in the salon as they can have a huge impact on the hair's texture and condition. My favorite is the Virtue Restorative Treatment Mask. It's a luxurious, deeply hydrating treatment that actively rehabilitates hair in need of extra care, immediately infusing shine, moisture and resiliency, leaving locks bouncy, vibrant and beautiful. If there's no Virtue treatment around, I recommend an oil treatment like one using almond oil.

What beauty tools do you use for optimum results? 
Harry Josh is my ultimate. It's eco-friendly, with a dual-filtration system that reduces energy consumption by 60 percent. The tool quickly dries hair and its dual-ion generator allows for both sleek and voluminous finishes, which is nice given that you can chose to switch between them.

Aging is a natural part of life, and as years pass, hair becomes thinner and weaker. Is there a particular regimen you recommend to clients for stronger hair in their 40s and 50s and further? 
The late 40s is often when women drop the ball on the condition of their hair, so that's when regular appointments for glosses and treatments are crucial. Salon treatments are invaluable, but I also recommend doing a mask at home twice a week to keep hair in the best possible condition between appointments. In terms of color, I would generally recommend keeping it slightly warm in tone, rather than a cooler, icier, ash brown finish, to create a softer, more youthful look.

Related: The Boldest Celebrity Hair Transformations of Summer 2019, From Harry Styles to Zendaya