Sets the gradient color for the Area charts. This is the end Color for gradient effect.
Enter a color by name, decimal RGB value, or hex RGB value. Prefix hex values with the pound sign, like #112233.
e.g. If you want a gradient effect of green to light green, set the area color to green and the area gradient color to light green.
Animated Charts have a default white gradient. For a single series chart, you can set this to a color which will be applied as the gradient. For multi series, white is the only gradient option. For no gradient on a multi-series chart, set this to any value.