DarkAdept, it's a figure of speech. To see someone (or something) in a different light means in a different way, not literally light. And it's usually a positive meaning, and sometimes expressed as, "in a new light." Sometimes the meaning is also to almost be noticed for the first time.
A good pop culture example are those cheesy high school prom makeover movies from the 80s and 90s, in which the nerdy or tomboy-ish girl may chat with her desired guy, but he always sees her as his pal. But then she lets her hair down, wears makeup, and dons a dress in stead of her usual jeans and t-shirt. Suddenly the guy realizes she's a beautiful woman, and more than just his lifelong pal. He uh ... sees her in a different light.