It's hard to tell from the pic, but the red tab has a lip on one side that you can usually pull with your fingernail. Be careful, they break easy. It doesn't need to pull all the way out, it will pull out a short bit, then stop. Usually they're easy, sometimes the little suckers don't move and they break no matter what you do.
Once you've got the red tab pulled back a bit, press down on the tab on the left side of the connector in the pictures and pull on the plug. It *should* come out.
My least favorite thing i had to do when I pulled out my 4.0 was try to release all of these connectors on everything.