function Rectangle(x, y, w, h) {
      this.x = x;
      this.y = y;
      this.width = w;
      this.height = h;
      this.bottom = this.y + this.height;
      this.right = this.x + this.width;
    }
Make sure that the color is an instance of Proton.ArraySpan, if not it makes a new instance

@method setSpanValue
@memberof Proton#Proton.Color
@instance

@param {Proton.Particle} particle
@param {Number} the integrate time 1/ms
@param {Int} the particle index