How to say buh-bye to brass and hello to modern, milky and metallic tones

There’s a hot new trend in haircolor and it’s really cool. Literally. Cool, milky and metallic shades that eschew any trace of obvious yellow, red or orange are in hot demand from brunette clients who are plowing through Pinterest and Instagram, uncovering the work of cool-meisters like social media superstar Guy Tang, and the cool blonde and tawny shades sported by beauties like Sofia Vergara and Jennifer Lopez. Suddenly—thanks to new formulations and new techniques—it’s possible to control even the darkest levels that always…