public function setColors($textColor = null, $fillColor = null) {
        
        // if the text color was specified
        if ($textColor) {
            
            // store it
            $this->textColor = new Color($textColor);
            
        // not set
        } else {

            // clear out the text color
            $this->textColor = null;
        }

        // if the fill color was specified
        if ($fillColor) {
            
            // store it
            $this->fillColor = new Color($fillColor);
            
        // not set
        } else {

            // clear out the text color
            $this->fillColor = null;
        }
        
        // chaining
        return $this;
        
    }