Blue.  Blue proves that the term suburban cool need not be an oxymoron. The space’s beautiful and sleek trimmings hint at the industral, but still manage to welcome and soothe.  That balance is echoed buy the employees, all of whom share a worldly knowledge of cutting and coloring but maintain a small-town, down-to-earth friendliness. Owner Paula Donovan works meticulous miracles with color, from rich, sultry reds to subtle, finely blended blonds. [10 Muzzey Street, Lexington, 781-862-2030.]