When you're looking for propagation lights, you'll notice they'll be labelled with numbers like 2700k or 6500k, which is a reference to the where on the colour spectrum the light given off by the bulb is. A 6500k propagation light (like our propagation LEDs) will give off a 'colder' blue light, perfect for early growth, while a 2700k (like these flowering LEDs) will issue a 'warmer' red light to promote flowering and fruiting.