Fade grayscale hover effect on images (grayscale to colored)

img {
     -webkit-filter: grayscale(100%); /* Chrome, Safari, Opera */
     filter: grayscale(100%);
}

img:hover {
     -webkit-filter: grayscale(0%); /* Chrome, Safari, Opera */
     filter: grayscale(0%);
}

You will obtain a better result using this function with Fade Effect on Hover for Images.

Source: http://www.w3schools.com/cssref/css3_pr_filter.asp