To change the color you must click once on the Black box or what ever you have created, then once that is done, just look over to the Right where you have all your colors and click on any color you want to change to, that should do it.
To change the Node just click on the Item once, then right click, you should see CONVERT TO CURVES, then Use the Node tool and click on the node and drag it to whatever position you want it to be.