code: public void setColorGradient(ColorRgba color1, ColorRgba color2)
      {
          setColorGradient(x, y, color1, x + maxWidth, y + maxHeight, color2);
      }
docs: Set a gradient color from point 1 with color 1 to point2 with color 2.
  
  @param color1 The first color.
  @param color2 The last color.