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 13 suffixes: title1-5, box1-3; flush, flushtop, flushbottom; plus standardcase and lowercase.
The Title suffixes control the styling of the module titles, matching the various article styles available, varying in shape, color and format. The Box suffixes change the background styling of the module, matching the settings in the Color Chooser. Remember, you can always combine suffixes together such as title2 box2, which will produce a colored module title, with a colored background.
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. StandardCase changes the title case to standard, with LowerCase change the title case to lowercase – Uppercase is standard, so no suffix required.