CSS3 Click Chart | CSS3 Browser Support and Information

RGBA Colors

Allows colors to be defined via RGB along with an alpha (transparency) setting.

.element {
    background: rgba(98, 135, 167, .5);
}

The background color of this paragraph is defined using an RGBA setting of rgba(255, 43, 0, 0.2)

IE9+, Firefox 3+, Chrome 2+, Safari 3.1+, Opera 10.1+