There are a few different ways to impart style into K2 SmartForms. Perhaps the most straightforward way is by using the controls in Designer. Apart from the selection of a style sheet, these controls allow for limited manipulation of style elements on objects placed within a SmartForm. For greater style control, one must consult the style sheets that comprise the themes.
There is, however, another way: One can create a style sheet and implement it directly on a specific SmartForm. The method is hackish and not entirely comfortable architecturally, but it can be done.
This document will walk you through the method used for this “style sheet injection,” and how to deploy the style sheets to other servers.