To Change the Color of a Color Key in Gradient Fill

From the Active Color dialog, select the Gradient Fill tab.
From the Type option menu, select the fill type.
From the Color Mode option menu, select Multiple Colors.
Click on the color (lower) button for the color key.
The Modify Color dialog opens.
Use the controls in the dialog to define the required color.
Click OK.
The dialog closes and the gradient is redisplayed with the new color included.