Light-emitting diode (LED) lightbulbs are all the rage when it comes to lighting. But shopping for LED bulbs can lead to unexpected surprises when you turn on the bulb for the first time; the light emitted can feel cold, clinical and not warm at all. When shopping for LED bulbs, the key words to search for on the packaging are "warm white" or "soft white." But more importantly, look for kelvin ratings -- a metric to measure color temperature. LED bulbs that are 3,000 kelvins or fewer cast a yellow light; any higher, and it'll likely be a cooler, bright white light.