For beginners I would suggest either the Staedtler or Faber Castell brand of pencils. These produce significantly better results than bargain bin pencils, provide good colors and allow you to try some simple shading and blending techniques. With practice the best coloring results can even be achieved with the most modest tools!
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.