code: public static SimpleColor getRandomColor(double opacity) {
          Random ran = new Random();
          int b = ran.nextInt(255);
          int r = 255 - b;
          return new SimpleColor(b + ran.nextInt(r), b + ran.nextInt(r), b + ran.nextInt(r), opacity);
  
      }
docs: 获取随机颜色
  
  @param opacity 不透明度
  
  @return {@link SimpleColor}