You apply the foreground color when you paint with the Brush or Pencil tools, and when you fill selections with the Paint Bucket tool. The color you apply to the Background layer with the Eraser tool is called the background color . You can see and change the foreground and background colors in the two overlapping boxes at the bottom of the toolbox. The top box is the foreground color, and the bottom box is the background color. The foreground and background colors are also used together by the Gradient tool and some special effects filters.
You can change the foreground or background color in the toolbox by using the Eyedropper tool, the Color Swatches palette, or the Color Picker.