Choose a combination of predefined colors here. Here are some examples. You can create any additional number on your backend theme, also can choose the background you want and four differents layouts.
The default Bootstrap grid system utilizes 12 columns, making for a 940px wide container without responsive features enabled. With the responsive CSS file added, the grid adapts to be 724px and 1170px wide depending on your viewport. Below 767px viewports, the columns become fluid and stack vertically.
Learn more: http://getbootstrap.com/