Okay, well, breaking magic into colours or shades isn't something I do often, except when trying to explain my path to someone else, too keep things organized really.
For example, I call myself a Solitary Eclectic Grey Witch (long title, I know) But I say that so other people know what I practice.
For shadow magic, you might be reffering to "black magic." And black magic isn't necsisarily a bad thing. It is often times considered magic that affects another's free will. It is a little dangerous and takes a well trained hand to do. It is often associated with doing something to curse or hurt another, but it isn't always like that.
You might also be referring to magic that deals with what some would call the "other side." Communicating with spirits and other entities.
I hope that was helpful!