Black and blue is not energy they are colours and are used in the visualization. When looking at energy you will need to know terms such as yin and yang, prana (lifeforce) chi ,ki,qi ,psi -same as prana generally. Let me give you a basic summary
Prana is an indian/sanskrit terminology for lifeforce energy which is absorbed via breath, this terminology is used in many languages and cultures like the chinese chi and latin spiritus.
Two spellings for the same thing , the chinese aspect of life force.
Ki is the japanese version for lifeforce , it also literally translates as wood which is a sub element of earth, earth is a living element (mother earth) and is known and revered by many cultures.
Psi is the modern term for psychic energy etc related to lifeforce.
Yin energy is a water element feminine based energy stored in the deep internals of the body , in places such as organs that perform transformation work such as the heart and lungs. Earth is another element associated with yin energy, yin energy is more dense than yang and creative and slow moving in the body's energy flow.
Yang energy is a fire elemental masculine energy,that is quick flowing and is held in the more external part of the body such as the muscles and storage/excretion organs such as the kidneys. Yang energy is also associated with air as an element.