Open the Choose Color dialog box.
Select the Custom tab.
Click the Add button. A new custom color will appear at the bottom of the list.
Select the named color and click the Edit field button to name the custom color.
TIP: Alternatively, you can double-click the Name field.
Click the color field to select a color. Select a color from one of the existing swatches, use the HSB (hue, saturation, brightness) color picker on the HSB tab, or enter an RGB (red, green, blue) value on the RGB tab.