•  Added body: People with limp locks may want to give color a try. That's because coloring plumps the hair shaft and can make hair temporarily thicker and with more body than before.

• Shine and dimension: Putting  color on the hair can create varied hues that pick up and reflect light differently. This can make the hair seem more vibrant and interesting to look at.

• More "pop": Just because a person was born with a specific hair color doesn't mean it is the best complement to his or her skin tone or eye color. Changing one's hair shade can make other attributes stand out more. Eyes may seem more radiant and skin less washed out. Experimenting with different shades can help a person find the best version of him or herself.

•  Natural options: Today there are hair dyes in many different formulations. There are also all-natural colors that deposit color into the hair, rather than stripping the cuticle to then add back color with chemicals. No matter the formula a person wants to try, a salon or over-the-counter product may be able to offer it.

Source: http://mcg.metrocreativeconnection.com/publish/sections/editorial-features-article.php?Benefits-to-Hair-Coloring-1522