API Reference > imodeljs-common > Symbology > GeometryParams > fillColor fillColor fillColor: undefined | ColorDef Optional fill color for region interiors. Set the same as GeometryParams.lineColor for an opaque fill. Valid when GeometryParams.fillDisplay is not FillDisplay.Never, GeometryParams.gradient is undefined, and GeometryParams.backgroundFill is BackgroundFill.None. The transparency component is ignored and should instead be specified using GeometryParams.fillTransparency. Defined in core/common/src/GeometryParams.ts Line 84 Last Updated: 12 June, 2024