Kant's deontological position

Kant identifies good will, or goodness for itself, as the defining factor of what is good. The importance doesn´t rely on the consequence your act of goodness will generate, but on your good motivations. Furthermore, the most important motivation would be that of duty. I don't really agree with this specific notion of the motive of duty, because then things as lying to a friend or family member in order to protect them, which would be done out of sentimental concern, would be completely wrong in Kant's stance because it's not expressing a good will. It seems to me as if he's seeing the concept of "good will" in absolute terms. There don't seem to exist any shades of grey between the white (duty motives) and black areas (other motives).