Module Variations allow for the individual styling of each module within a position, without it being global. Code wise, this is achieved by adding a class into the module code which loads from the Module Class Suffix field in the Module Manager. The theme CSS adjusts accordingly.
Enter any available suffixes at Extensions → Module Manager → Module → Module Class Suffix
There are 14 suffixes: bg1-5, title1-5, flush, flushtop, flushbottom & basic.
The BG and Title suffixes load their coloring from the Color Chooser options of the template, if blue is the header color, bg1 will be blue. bg1 loads the header color; b2 loads the feature color; b3 loads the main surround color; b4 loads the main body color; and b5 loads the footer color. These are available in all the main body areas: MainTop, MainBottom, ContentTop, ContentBottom and Sidebar. The suffixes will work in Top, Header, Bottom and Footer, but may not be as aesthetically pleasing, depending on your color combination.
Flush will disable all padding and margin to the module for a tighter fit, with FlushTop and FlushBottom disabling the margin/padding for the Top/Bottom parts of the module respectively. Basic removes all image based styling from the module.