The color to use when for data points in a Geochart when the location (e.g., 'US' ) is present but the value is either null or unspecified. This is distinct from datalessRegionColor, which is the color used when data is missing.
Default value
Theme: A color compatible with the theme (if a theme is present) that blends with the geochart background.
Valid values
Color in #RRGGBB hexadecimal format.
