Well, of course, contact lenses can not really change the color of your eyes. Actually there are some types of contact lenses which are named as colored contacts. Generally speaking, colored contact lenses are used to change the color of your iris, either giving new hues to the original color by means of a barely colored lens or modifying it massively with intensely colored one. But when you take off the contact lenses, your eyes will look normal. On the other hand, color of the eyes can change with the different emotions. If you are embarrassed or excited, your eyes will turn to red ones.
Eye color depends on the quantity of coloring matter in the iris. The more the quantity of coloring matter is, the deeper the color of the iris is, and the more black the eye color is. On the contrary, the less the quantity of coloring matter is, the shallower the color of the iris is, and the lighter the eye color is. Contact lenses can change the quantity of the pigment in the iris, hence changing the eye color temporarily. I advise you not to wear contact lenses for a long time because they can cause many eye diseases due to lack of oxygen.
There are two main kinds of contact lenses. One is transparent contact lenses and the other is colored contact lenses which may make you change the color in the eyes. However, whatever kind of contact lenses will not change your original real eye colors. If you have such change, you should go to the hospital to check the eyes fully.