The usefulness of LED Lights cannot be overemphasized. Most of these kits have blue LED lights, and they work effectively in the whitening of teeth. They produce an optimum amount of heat that would be suitable to remove stains â even those that have existed for years. However, there is a duration for its application â while some take about 8 minutes, others last between 30 minutes to 1 hour. Regardless, you need to be consistent with treatment, so that it could reach its full potential to give you all shades of white.