The Red Eye Tool desaturates the center portion of the selection that you create by clicking-and-dragging the tool around the eye. Sometimes you may need to create a second selection to remove the red color
Learn how to quickly erase a Photoshop background using the Background Eraser Tool.
Adobe Photoshop Guidebook
One of the things you often see us talking about when explaining Photoshop techniques is layer masks. If you are new to using Photoshop and haven’t had much experience in the interface, you may be totally lost as to what this means. Here you can learn everything that you need to know about layer masks, so you can start using them with confidence!