What's the best formula for a mostly gray client who wants her color to last at least six weeks?

Aura Friedman

"The best way to avoid a fast re-growth is to match your formula closely to your client's natural hair color," says Wella Professionals' Lead Color Ambassador, Aura Friedman.

It's also important to keep the hairline lighter and softer. This will keep their color looking as natural as possible, and re-growth to a minimum, especially because people who are mostly gray tend to have a mostly gray hairline, and the hairline is what people see first. Use Wella Professional's Koleston Perfect new Pure Naturals to cover primarily gray hair. This product will give good, but slightly translucent, coverage. It is just enough to cover gray but not too opaque to make the re-growth so obvious that it will show up as quickly as some intensive permanent color. The Pure Naturals will cover the gray, give it a little lift, and will keep the tones cooler and more natural. This will allow the natural base color to blend in better when the natural color grows out. -Aura Friedman

Estelle Baumhauer

"My biggest challenge with lasting color that covers gray is not about hair color-it is reminding clients that hair grows and their new hair has no dye," says colorist Estelle Baumhauer, who has worked in salons such as Warren-Tricomi in New York and Dessange in Paris. By nature, contrast between gray hair and dark hair re-growth is more noticeable.

"Regardless of color, I always pay attention to the gray percentage in the hair. I add more base into a formula for people with a higher percentage of gray to ensure better coverage and natural-looking results. Dark brunettes tend to dye their hair more often because gray is visible more quickly. Overall, coloring with their original hair color or one shade lighter will create a lasting and natural effect.

"For brunettes, my advice is: Choose warm browns and chocolate tones, which are easily absorbed by gray. For redheads and strawberry blondes, shades of copper and auburns look best on gray hair. They appear natural looking and leave highlight transparencies. Blondes hold color the longest because the re-growth contrast will be less obvious. For blondes, soft colors like beiges and golden tones will create harmony between the roots and the ends. I formulate color with more base depending upon the level of gray and tones that complement their skin tone." -Estelle Baumhauer

Jennifer Jordahl

"When it comes to covering stubborn gray hairs we look at it in a couple different ways," says Jennifer Jordahl, senior colorist at Red 7 Salon in Chicago. "A permanent hair color line like Kolsten Perfect by Wella will give you great, full-gray coverage, but that can also make the re-growth much more noticeable when the client's natural hair starts growing back. Using a demipermanent color like Color Touch by Wella will give more blended coverage, not 100 percent, but a more blended line of re-growth will make the color seem to last longer."

"I like to use a demipermanent color, when I can, so clients may go longer between appointments. Also, keeping in mind, the closer the color you choose to your client's natural shade makes it seem to last longer because there won't be as much noticeable re-growth. I also like to always add some warmth to the color formulation as natural hair color and grays tend to be ashier. The warmth will brighten them up and reflect the light better to add shine to the hair." -Jennifer Jordahl