colorChangeF(tf_mcHT_2.tf,0x000000);

I want to change the color of a text. Below is my code. Everything works except for colorChangeF(textNumNowCol,0x000000);

It works when I try replacing

colorChangeF(textNumNowCol,0x000000);

with

colorChangeF(tf_mcHT_1.tf,0x000000); or colorChangeF(tf_mcHT_2.tf,0x000000); or colorChangeF(tf_mcHT_3.tf,0x000000); ....

/////first part of the code:

var textNum:Number = 1;

var tf_mcHT:MovieClip = tl.attachMovie("tfID"+typeNow_tx.text,"tf_mcHT_"+textNum++,tl.getNextHighestDepth());

textNumNow = textNum -1;

////second part of the code:

textNumNowCol = "tf_mcHT_"+textNumNow+".tf";

trace (textNumNowCol) // shows correctly as tf_mcHT_1.tf or tf_mcHT_2.tf or tf_mcHT_3.tf...

colorChangeF(textNumNowCol,0x000000);

{   _root.CN5.text= _root.CN55.text="BLACK"}

{   _root.defTC.text="0x000000"}

}

function colorChangeF(mc:MovieClip, col:Number):Void {

    mc.c = new Color(mc);

    mc.c.setRGB(col);

}