The problem with the Paint Bucket tool (which you can select by pressing G and then Shift+G) is that it's hard to get the Tolerance value just right. You usually end up choosing Undo several times and resetting the Tolerance value until you find the value that colors only the pixels that you want to color. Overall, the Paint Bucket is a poor tool for filling areas in Photoshop. If you select an area in your image by using the Magic Wand tool, which chooses pixels of similar color surrounding the cursor and then fills the area with a color, you produce the same effect as with the Paint Bucket, and you have more alternatives at your disposal.