The domain objects of the Lucy drawing add-on are TLcySLDDomainObject instances. These domain objects contain both the geometry and the style of the object. See the reference guide of the drawing add-on for more information.

The style is a TLcdSLDFeatureTypeStyle and is accessible through the getStyle and setStyle methods.

Thiw example shows how to retrieve the style of a polygon object, and update the fill color:

static void updateFillColor(ILcdModel aDrawingModel,
                            TLcySLDDomainObject aPolygonDomainObject,
                            String aColorValue) throws Exception {
  //Since we are modifying the domain object, we need a lock
  try (TLcdLockUtil.Lock lock = TLcdLockUtil.writeLock(aDrawingModel)) {
    //Retrieve the SLD style from the domain object
    TLcdSLDFeatureTypeStyle currentStyle = aPolygonDomainObject.getStyle();

    //To update the style, we need to set a new TLcdSLDFeatureTypeStyle
    //instance on the domain object
    //Therefore, we first make a copy of the style
    TLcdSLDFeatureTypeStyle copy =
        TLcdSLDFeatureTypeStyleDecoder.decodeFromString(TLcdSLDFeatureTypeStyleEncoder.encodeToString(currentStyle));

    //Retrieve the TLcdSLDPolygonSymbolizer from the SLD style
    TLcdSLDPolygonSymbolizer polygonSymbolizer = findSymbolizer(copy, TLcdSLDPolygonSymbolizer.class);

    //Adjust the fill color
    TLcdSLDFill fill = new TLcdSLDFill();
    fill.setCssParameter(TLcdSLDFill.CSS_PARAMETER_FILL, new TLcdSLDParameterValue(aColorValue));
    polygonSymbolizer.setFill(fill);

    //Replace the style on the drawing domain object with the updated copy
    aPolygonDomainObject.setStyle(copy);

    //Indicate to the model that the object has changed
    aDrawingModel.elementChanged(aPolygonDomainObject, ILcdModel.FIRE_LATER);
  } finally {
    aDrawingModel.fireCollectedModelChanges();
  }
}

Consult the SLD documentation for more information about working with SLD styles.