code: function (x, y, width, height) {
              var color = this.currentColor.clone();
              this.currentColor.copy("#000000");
              this.fillRect(x, y, width, height);
              this.currentColor.copy(color);
              me.pool.push(color);
          }
docs: Erase the pixels in the given rectangular area by setting them to transparent black (rgba(0,0,0,0)).
  @name clearRect
  @memberOf me.WebGLRenderer.prototype
  @function
  @param {Number} x x axis of the coordinate for the rectangle starting point.
  @param {Number} y y axis of the coordinate for the rectangle starting point.
  @param {Number} width The rectangle's width.
  @param {Number} height The rectangle's height.