Color cast, even though scanner is calibrated

Using IT8-calibration should convince any scanner to scan with true colors. In theory it works, in practise sometimes not. There are some cases, when calibration shows only little or no effect at all.

Case1: Scanning Negative Film

IT8-Calibration is a method designed for colour slides exclusively, not for negative films on any kind. That's why it has not the desired effect when scanning negatives. 

Case2: Cheap Scanner

If you are using a scanner of inferior quality, you can calibrate it as much as you like, but you will never convince it to reproduce colors properly. It doesn't help when you buy additional software in this case, invest your money better in a proper scanner.
 

Case3: Slides with Color Casts

If your images have color casts, calibration will not exactly produce the desired efffect. You will scan you image in true colors, but that of course means, the color cast of the image will be reproduced 1:1 by the scanner. You don't produce the desired neutral colors. Even nowadays scanner don't have so much intelligence that they identify and eliminate the color cast reliably. You have to do this in post processing with a correction method like Digital ROC or with Photoshop. Even though Digital ROC ships with Nikon Scan, you should better apply it after scanning, as it can be difficult to find an adequate setting.