EL Wire, because of the properties, can never truly change colors from Green to red, or blue to orange. EL Wire is made from a colored plastic tubing which cannot change colors. What is possible however is to alter the frequency at which the EL Wire is powered. This enables the wire to change a different hue when it is powered from a different frequency. Take a look at this handy how-to guide and have fun with EL Wire projects!
UPDATE 2015: While EL Wire technically cannot change colors, Laser Wire can. It uses laser technology which is similar to fiber optic lighting, but allows for more flexibility, brighter light output, thinner and lighter weight product. Because there is a light source at one end, it allows to change out the laser module easily if needed.