setWhiteBalance
This function is useful when you need to use the absolute color information in the images.
As you might know, the automatic white balance is usually performing correctly. Nevertheless, colors perception drifts with the light temperature (expressed in °K) and will still have effect on the automatic white balance, even if this mode aims to reduce this effect. Moreover, the automatic white balance can't work properly when there is a dominent color in the image. So for instance, finding a blue ball using its color will be a problem when the automatic white balance is active, as this blue shape will delude the system trying to fix the correct lengths for a neutral grey.
A solution is to look at a white or grey pattern used as a reference and to disable the automatic white balance. This is what is done when calling setWhiteBalance function: NAO looks at his hands and freezes the white balance lengths.