Every website has a purpose. Depending on the type of website you have and your goals, your design needs to provoke your audience to act in some way. Buy a product, sign a petition, read an article, share with friends, and so on. One way of doing this is with contrast. The colors we use, the amount and types of content you display, can have a big impact on what our viewers see and do. When you have a very specific direction you want to steer your viewers in, the more contract in the right areas, the better.