For some who either actively seek to develop the ability to visually experience energy, those who are born with the ability, or those who simply develop it through spiritual exploration, it is certainly possible to "see" energy.
Colors, patterns, etc. are all simply the mind trying its hardest to provide a sensory perception to something for which we have no sense. As such the patterns witnessed generally put forth a sort of "impression" that hits upon your instincts, intuition, etc.
The result is a gut feeling about the energies that you have viewed, created by the patterns that you have "seen." Thus black energy may, to some, be viewed as negative energy while to others might only be a representation of shadows and night. White energy may be positive energy, or it may just be a representation of the moon as a magical force or a manifestation of "light."
Truthfully, it all varies a great deal with whatever tradition your magical education is rooted in and what the people around you call it. It usually boils down to the same thing though.
Just my two cents.