Whilst most colored pencils are wax based, some brands use an oil based lead, like Faber Castell's Polychromos. These pencils are very soft to apply color so will cover every fibre of the paper with their bright hues, but they are also very expensive and should only be considered if you are looking to take your art to the highest level.
Psychologist Gloria Martinez Ayala tells the Huffington Post that coloring triggers and stimulates the brain areas associated with motor skills, creativity, and the senses. Coloring helps to calm the part of our brains called the amygdala, which controls our emotions and stress. Simply put? Coloring takes our minds off our problems, and as a result leaves us feeling much more relaxed, rested, and at ease. Furthermore, experts say that concentrating on a coloring book lets us mentally escape by bringing back memories of childhood, a less stressful time for many of us.