Jon Charles, left, applies subtle coloring, selectively reducing the gray for Ross Fefercorn at his Uptown salon.

Among the sundry ways in which life sorts itself into lists labeled Fair and Unfair is the way in which we regard gray hair on males and females. Generally speaking, men gain the adjective “distinguished,” while women are saddled with “mature.”

Yet, the Fair/Unfair lists also include the notion that it’s acceptable for women to get their gray painted away in salons, while men should just suck it up.

Now there is a middle ground – dare we call it a gray area? – called “gray reduction” and it’s keeping chairs filled the Jon Charles Salon in Minneapolis.

Charles said he’s been working on this concept for 20 years, about as long as he’s been styling hair.

“My joke is that I’m the only straight man who, when I meet a woman, looks up instead of down because I’m checking out her hair,” he said.

Charles is guided by what he calls the three rules of male hair color.

1. No Elvis black. “It’s not acceptable – unless you’re on the professional gambling circuit.”

2. No orangey or brassy. “No one should be orangey or brassy, but especially not men.”

3. No line of regrowth, or what bottle blondes call dark roots.

“Is there anything wrong with gray hair? No,” Charles said. But it’s a fact of life that people make judgments based on appearance, and that in a worrisome economy, the vibrancy of youth can trump the wisdom of age.

His is not an isolated observation. Sales of men’s hair dye have soared in the past 15 years as guys have experienced the sort of hubba-hubba scrutiny that women have fielded for centuries. From People’s “Sexiest Man Alive” to TV’s “Queer Eye for the Straight Guy,” men are learning that Bo Derek wasn’t the last person to be measured against a numerical scale.