@Override
    public void write(JmeExporter ex) throws IOException {
        super.write(ex);
        OutputCapsule oc = ex.getCapsule(this);
        oc.write(color, "color", ColorRGBA.White);
    }
sets the color

@param color the desired color (default=(1,1,1,1), alias created)
jme3-effects/src/main/java/com/jme3/post/filters/ColorOverlayFilter.java