This is the color control area of the toolbox. The color control area consists of the foreground color swatch, the background color swatch, the fill color swatch, and the reset color icon.
The default foreground color is black. To change the foreground color, click a color on the color palette. The foreground color is used by the Text tool and all paint tools.
The default background color is white. To change the background color, Ctrl + click a color in the color palette. The background color is shown when you erase portions of the background with the Eraser tool.
The default fill color is black. To change the fill color, right-click a color on the color palette. The fill color is used by the shape and fill tools.
By clicking the reset color icon, you go back to the default foreground, background and fill colors.