This dialog is used to set the text of the legend and color of selected values of Custom Plots. Each value selected will be listed along with the current legend text and color. The first time the legend is set for a value, the default legend text will appear. There is no default color, so the color must be set.
Resetting the legends from the Custom Plot Properties dialog resets the text of the legend to its default, but it does not change the color that has been set.