I created an additive graphic style that includes a few effects, and applied this style to a few objects.
Now I'd like to make a change to this style and apply the change to all objects. For example, instead of an outer glow of 1px (which was in the original graphic style) I would like to change it to 5px and apply to all the styled objects.
Is it possible to edit a graphic style? If not, how would you perform this task?
There isn't a direct way to edit a graphic style. varun's answer will handle the situation where all of the objects are in the same document.
If you want to save a style so you can use it again in other documents, select the layer that has the modified style applied and choose "New Graphic Style" from the Graphics Styles panel flyout menu. It will then be available in new documents that you create (handy when you're building multiple documents for a website comp, an ad campaign or corporate identity).