There are several stock style sheets including but not limited to:

default.css
alphacube.css
CustomStyle.css
FormComponentsBehavior.css
UserGlobalStyle.css

Whenever Luminate is updated, almost all of these are overwritten. As such, it is not recommended to change most of them as the changes will be erased when Luminate is updated. The only default style sheet that is not overwritten is CustomStyle.css.

If it is necessary to override a style that is defined in one of the non-Custom css files, define that style in either the CustomStyle.css or create a new style sheet and define that style in the new style sheet.

Why create a separate style sheet instead of using CustomStyle.css? The CustomStyle.css exists in every Luminate page. If it is desirable to only have the style sheet apply to certain pages, then create a separate style sheet and reference it in the desired pages or Page Wrappers.

As a demonstration, this is how you would modify the CustomStyle.css file in your FTP:
  1. First, you will need to access your FTP (BB735774)
  2. Open the .K2-css folder
  3. Download the CustomStyle.css file to your computer and make your desired changes (keep the original file on your computer as a backup)
  4. Upload the modified file back in to the .K2-css folder