I have Been studying by myself and trying to figure out what a colorist need to work as a professional colorist, under some great colorist and publishers suggetions, I found out some cool answers that now I use to color my work as you can see it.
A Colorist Must...
1 - have knowledge of color theory.
2- Create a conscious and consistent lighting.
2a. Study Light and Shadows.
2b. Light Source.
2c. light intensity.
2d. Multiple Sources of Ambient Light.
3 - Handle a Large Variations of Styles and Techniques
4 - Use colors to complement the story.
4a. highlight the focus of the scene.
4b. progression of the scene
4c. scene transition
4d.Action.
4e.Quiet Scenes.
4f.Mood of the Scene.
4g. spatial separation
4h. balance between character and environment
4i. a emotional and subjective color palette
4j. atmosphere.
5 - Render Characters, Faces, Objects, Background and Textures.