This graph displays area plot of two datasets where a horizontal color gradient has been applied. These two datasets has been plotted as a stacked area, that means the second column of values displays as an area graph that is stacked on the first area graph.
To plot each of the data plots so that the area between the data plot and the "From" Y axis value is filled, select Graph: Offset Grouped Data in Layer: None.
Origin supports both one-color and two-color gradient fill control,
which can be used for the page background or layer background of any graph,
and also for the pattern color and fill color of a Column, Bar, or Area graph.