The Wireless charging pad uses an LED indicator to alert you if you have the phone on the pad incorrectly. A green light means that everything is copacetic while a yellow light means that something is amiss. The pad is compatible with all Qi enabled smartphones. Last year, Samsung offered wireless charging capabilities for the Samsung Galaxy S III.
You can now wirelessly charge your Samsung Galaxy S4 using the special back cover (L) and the wireless charging pad
source: Samsung via Pocketlint