Color Temperature is a real measure, but it is being improperly used to claim improved seeing. Legitimate bulb manufacturers do catalog the color temperature of their products in technical literature not usually distributed to consumers, because scientists and engineers can use it as a convenient proxy indicator for filament luminance. But it has no predictive value for the performance of an automotive headlamp, nor does it indicate how well you'll be able to see. The idea being sold with these "Kelvin ratings" is that the light is closer to natural sunlight. As with many sales claims, there is a small kernel of truth here, but it's cancelled out by the smoke and mirrors. Noonday sunlight does have a much higher color temperature than most uncoated headlamp bulbs, but there are a great many other differences between sunlight and headlamp light, as well. Not only that, but the Color Temperature rating is really valid only at extremely high light intensity, such as that produced by the sun. At the lower intensities produced by most electric lamps including headlamps, the rating no longer says much about the light, but only allows a limited, referential comparison of different light colors
