Are the objects in the Library saved as an uneditable file?

Hi,

I'm still fairly new to Adobe. Over the past month, I've been adding my artwork to the Library (through Illustrator, PS, and ID). Today I tried to drag and drop something in that library expecting to be able to edit the color of the image I was importing (if that's the right word), but I couldn't. I could scale it, though. 

The items in the Library, what perameters are we able to edit when placing them into a document? Is there something I can do when adding an artwork to the Library to increase the flexibility? (Right now, I've been grouping all the files before I drop them into the library.)

Thank you,