Prova un po' così:
codice:
MovieClip.prototype.flashing = function()
{
this.params = arguments[0].reverse()
this.x = 255;
this.col = new Color(this);
this.i = this.params.length - 1;
this.intervallo = setInterval(this, "cambiacol", this.params[this.i]);
};
MovieClip.prototype.cambiacol = function ()
{
this.x = this.x - Math.ceil(1 / this.params[this.i]);
if (this.x <= 0) {
clearInterval(this.intervallo);
this.x = 255;
this.i--;
if (this.i >= 0) this.intervallo = setInterval(this, "cambiacol", this.params[this.i]);
} else {
this.col.setTransform({ra:'100', rb:this.x, ga:'100', gb:this.x, ba:'100', bb:this.x});
}
};