Good contrast can make sites appear crisp and organized, whereas poor contrast blends the content into mush. Contrasting elements allow for the user to figure out which page areas are related and which are totally separate, so be sure to differentiate your elements and page sections. Contrast attracts attention to important content.
Contrast is the differences that make an object distinguishable from surrounding content. That means that your graphics, “call to action” elements and anything else that you want to stand out should be different or contrast with the print to make them more noticeable.
Elements that are not related should be very different because making things only slightly different might confuse the viewer into believing there is a relationship where really one does not exist. Contrast in your design livens things up and makes things easier for people to understand.