Here the contrast is working well with each of the elements. The model is able to be the star of the cover while the type around him is still legible. The pops of color contrast the neutral colors and draw the eye in. Adding to that is the contrast in type size, which creates a hierarchy of what to read. Eventually leading the viewers eyes around the entire cover.
This is an example of poor contrast. It is over saturated with colors, photos and type. There is no room to breathe in this cover, so the viewer is unsure of where to start. Most of the type is the same size in competing loud colors with no contrast to demand hierarchy. Then the collage of people's heads each require attention, building onto the confusion. The color blocks of separation do not aid in creating contrast for the viewer.