Vibrant comes from French vibrant, from Latin vibrans, present participle of vibrare (“to vibrate”). 

The earliest known use of the adjective vibrant is in the late 1500s. OED's earliest evidence for vibrant is from 1572, in the writing of John Bossewell, author.  

A vibrant person shows great life, great activity, and great energy. A vibrant person is alive in the deepest part of his or her soul and flourishes in every season of life. 

A vibrant color need not necessarily be as saturated as a bright one, it could be much paler but still be pure and very powerful.  Fluorescent colors would fit the bill here, but there is another way to think of vibrant color(s).