yup, the kelvin rating is only a measure of light's "color temperature". here's a few charts the better show the color scale. i find that 6500k are too yellow for my tastes, so i go with 10,000k for my tank. the color is not really as blue as shown, but you get the idea...
this one is more accurate id say
and from vehicle HID kits
this one is more accurate id say
and from vehicle HID kits


but really though, once you get everything dialed in right and you have the algae under control, its get pretty simple.