Ombre is a technique where the hair is darker at the roots, and lighter at the ends. A lot of the time this occurs naturally after someone has gone too long between touch-ups, but it also happens purposefully these days, since it became a fashion statement. Ombre is possible on any color of hair, and is very easy to do yourself on natural or color-treated hair. Red ombre hair is one of popular color for ombre these days. See: How To Get Ombre Hair.