Each Led Status on your controller is showing a different status. If you want to know the meaning of each color follow the steps in this tutorial.
Step 1. Green color
■ The green color means ready state for HTC Vive
■ If the color of your controller is white than the Vive is ready ( Vive Pre developer kit only)
■ If the color on your controller is blue than your controller is connecting
■ If your controller does not change color go to SteamVR > Devices > Pair Controller
■ Your controller is in pairing mode
■ This color is showing you that you controller has low battery.
■ Plug your controllers into an outlet with the micro USB cord and the power adapter so you can charge them
■ Your controllers are charging.