code: public void setStartCornerColor(Color color) {
          if (startColor == null) {
              startColor = new RGBColor(0.0, 0.0, 0.0);
          }
          setGradation(true);
          this.startColor = color;
      }
docs: Sets the start point's color for gradation.
  
  @param color The color of the start point.