magick is intent, not colour, so if you study 'the basics' [pinned articles in the General Information section] and get a strong footing with them, you can cast what would be considered 'black magick' as the only difference is the emotions you charge and what you visualize.
As has already been stated, it is all about intent and not colour.
It is far less "black and white" as people assume at first, for example: a spell to improve your job prospects may assist in you getting a job, but someone else who may really need to the job will lose out. Any spell, ritual or other magickal practice has the potential to be both positive and negative, that is where the concept of "black and white magick" can get a little, murky.
There are some great forums on this site that can help you get started on your journey: