An example of poor contrast: everything has the same visual weight.
Imagine what it would be like to go through life without any flavors at all: no saltiness, no sweetness. Everything would just taste the same, day in, day out. You would get a little bored, right? Well, the same applies to a layout: if everything looks the same, the reader eventually gets bored and moves on. You have to provide some visual interest, some sort of visual texture for the reader to enjoy.
What is contrast?
Contrast is the accentuation of the differences between visual elements in a design. A lot of people think contrast only applies to color, but it can be applied to any design element. It occurs when 2 or more elements look dramatically different from each other.
Much better contrast: the biggest circle provides a focal point.
Why Use Contrast?
The principle of contrast is one of the fastest, most reliable means of adding visual interest to a page. It is usually used in concordance with emphasis to keep things on the page from looking too much alike. When that happens, the reader can’t tell what he should look at first. What is the most important? What is the background?
Without any contrast, the composition is bland, uninteresting, and difficult to read: it’s just one big, undistinguished blob. Who’s going to wade through that?
A layout organized using contrasting elements.
On the other hand, look at how a few simple moments of contrast can help add distinguishable moments of differentiation: the large headline and turtle image are the obvious focal point, and the smaller subhead is the supporting detail. Notice the subtle influence of the rule lines as well.
