COLBIE AND LILY.B: Skin care lines and singers apparently make great music together. Nivea is singing a happy tune with Rihanna, and Proactiv is rocking out with Katy Perry. The latest pairing of a singer with a skin care line is Colbie Caillat with Lily.B Skincare. The Grammy Award winner, whose chart-topping pop hits include “Bubbly” and “Brighter Than the Sun,” has signed a multiyear agreement to become Lily.B’s first official celebrity spokeswoman. “The Lily.B line is simple, made of natural ingredients, without the use of parabens, dyes or fragrances,” stated Caillat, “and I really love that they don’t test on animals.” Caillat will promote Lily.B in print, online, in-store and through social media materials, and hold a series of appearances for the brand. She is going on a 50-city concert tour with Gavin DeGraw starting May 25. Lily.B is a natural skin care line aimed at women 22 to 38 years old, which launched in 2010.