Need help with text format

I am trying to set one of three formats to a dynamic text box in a movieClip

pfd_mc.crsTxt_mc.crs_txt.text = "150";
pfd_mc.crsTxt_mc.crs_txt.setTextFormat(nav);
var ils: TextFormat = new TextFormat();
ils.color = 0xFFFF00;
var nav: TextFormat = new TextFormat();
nav.color = 0x00FFFF;
var tcn: TextFormat = new TextFormat();
tcn.color = 0xFF00FF;