Adding EM-Categories to body-tag

sorry, can I know where is this; in the single category page and/or category listing ?

I need it in the single event pages, if it also works in category listings would also be nice.

The placeholder you need is #_CATEGORYCOLOR. You can access it within the category PHP templates by using code like this:

global $EM_Category;
echo $EM_Category->output("#_CATEGORYCOLOR");