Black can make a front door elegant and dramatic. It works well with any and every other color, making it extremely versatile. It can also toss a challenge your way. If you don't have enough contrasting colors as a backdrop, black can hide the entry or make it feel too dark -- not very good for your home's curb appeal. Here are examples of black front doors done beautifully right, along with sample palettes of complementary exterior colors.
For examples, head over to Houzz.