This is where to change the default colors of worker. Simply click on the Foreground or Background buttons beside the item you wish to change the appearance of. The color palette as defined in the Palette section will appear.
Working with the panel colors can get a little confusing, especially if you mix up the meanings of selected and active. Active means any file or directory that the cursor is currently on. Press the up or down arrows and this should be apparent. Selected is any file or directory that has been explicitly selected by you. Press the insert button on your keyboard to see this.