The lightness or darkness of a color refers to:
Intensity
Color
Contrast
Value

it's all focused on the way you angle and put all of these this in pespective. say you wanted you artwork to be famous, you would want to align and put all of these into grasp. the imagery give off a good descriptive matter. proportion is aligned with the color and mood. balance is how you place everything and if there is too much or too little of. design is the main thing if you want your art to be amazing

virtual smiles! : )

~mqddie