Here comes the science bit!
Kelvin is a measure of the wavelength of the light which represents the coulour 7500 kelvin is almost the same blue as HID lights or Metal Halide type bulbs new Vauxhalls and beemers.
1500 K Candlelight
2680 K 40 W incandescent lamp
3000 K 200 W incandescent lamp
3200 K Sunrise/sunset
3400 K Tungsten lamp
3400 K 1 hour from dusk/dawn
5000-4500 K Xenon lamp/light arc
5500 K Sunny daylight around noon
5500-5600 K Electronic photo flash
6500-7500 K Overcast sky
9000-12000 K Blue sky
Low color temperature implies warmer (more yellow/red) light while high color temperature implies a colder (more blue) light. Daylight has a rather low color temperature near dawn, and a higher one during the day. buy 'em and blind the f*ckers that blind u!