Principles of design
Contrast art refers to the arrangement of opposite elements light vs. dark colors, rough vs. smooth textures, large vs. small shapes in a piece of art.
This is an example of contrast because the left side of her face is more darker then her right side, and the left eye is a different color.
This image is an example of contrast because the flames turn into a different burning flaming red, and then in the bottom it turns a really dark but yet reflecting color.
This image is a example of contrast because not only is the picture its self going from a darker to a lighter shade, but also the women's face in the image is a different kind of texture, like more smoother then the background.