No doubt the Nikon has some problems, but then so does the Canon. Both of them are incorrect in their color rendering, but the Nikon camera usually tend in one direction (pulling yellow, orange and red towards the "clockwise" if you think of colors as in a color circle) and Canon in the other. Canon usually pulls orange, red, purple and blue in towards the red center, making yellow>orange and form the other direction; blue>purple.
Neither camera is usable for "good" color straight out of the box in full automatic settings, but it could be argued the Canon errs in a more pleasant way (on which I agree).
Absolute color temperatures, in the way that camera manufacturers indicate them by "Kelvin" simply does not exist. At least they're very rare, the one true example you can find out in reality nowadays are high-efficiency halogen bulbs. Anything other than this has a +/- green/magenta tint away from the CCT line of "Kelvin color temperature".
Shooting in the most common light indoors today, fluorescents, you have a very distinct tint towards green if you don't compensate for the errors induced by the light. This is exactly what SHOULD happen.
My guess is that Canon partly compensates for this out-of-the box, which can be seen if you shoot something in true 3000K light - here the Canon cameras turn very much to red.
That said, Canon is vastly better in the way it allows you to download color-compensation into the camera (it's the jpg-engine that handles raw-color conversion for movies and LV) via the Canon Profile Editor. If you want production quality color straight out of the camera, this is the only way to go. Nikon has no such possibility, you need to correct colors in post-production to get accurate results. This in-camera adjustments only allow for WB finetuning, not for real color correction.
WB is not the same as color correction. It is the first part of color correction, but the main part of heavy lifting happens later, in the color conversion of the raw file. WB balances the average strengths of three unknown raw channels, the rest of the profile translates the result into human-vision based color.
