There are no colors in magic. All magic is simply the manipulation of the energies surrounding us to achieve the goal we seek. Think of magic as being a bit like electricity. We can use electricity to light our homes and to keep us safe, or we can use it to kill someone. But we don't talk about "black electricity" or "white electricity. Magic is the same, it can be used for good or for ill, but it is still the same energies. The only difference is what is the intent of the person using those energies.
Witchcraft is one form of magical practice; however, there are many other forms out there. There are sorcery, ceremonial magic, chaos magic, kabbalistic, tantric, witchcraft, etc. All use the same energies but approach that use from different perspectives.
And to correct a later statement, " black magic " is not one form of witchcraft. As I've already said, there are no colors to magic, nor are those who practice witchcraft doing something evil.