Black is a 'controlling' colour, it is very powerful and grounded energy, it works really great for defensive and protective purposes especially coupled with the usual white-gold protective aura, you just have to know how to direct it.
When it comes to defending against negative energy it acts like a force-field where negative and hostile energies struggle to breakthrough, a powerful barrier that holds it's ground. Black binds and breaks up these negative forces like the destructive energies of Saturn in that it reverse engineers them and tears their structure apart completely undoing them and this can protect against thoughtforms. Black can be used to destroy bindings, blockages and barriers as well, I've used it in workings to help free my soul, it is not an evil colour like xians try to make people believe.
When working with black energy to protect against negative energy you want it to only block and protect you from unwanted and negative energy, you don't want to prevent positive energy from coming in such as when you want to draw in empowering energy from the sun, so just direct it so to allow positive energy that you desire to come through.
If not directed properly you could end up trapping negative energy inside of you unable to escape with cleanings, so before you build any kind of protection around yourself especially with black energy, clean your soul and aura as thoroughly as you can first. When visualizing black energy, visualize it as shiny black energy, like a glistening obsidian or onyx stone. Adding the shiny factor helps with focus on the clean and positive properties of the black energy.
You can build a black energy aura outside of and around yourself to protect you against negative energy and negative forces. This can be especially enforced around the head if you're dealing with psychic attacks as it will help defend against these greatly and has worked very well in my experience, just ensure these protective black auras are strong, powerful and shiny.