When you have 60 icons I’d rather colorize the filled elements instead of using a color transform.

You could recursively walk your fxg icons and check for filled elements and then colorize them.

Something like this
Recursively seek for nested FilledElements and set the fill color to the current color

private function fillIconWithColor (el:IVisualElementContainer, color:uint):void {
for (var i:int = 0; i < el.numElements; i++) {
var elem:Object = el.getElementAt(i);
if (elem is IVisualElementContainer) {
fillIconWithColor (IVisualElementContainer(elem), color);
} else if (elem is FilledElement) {
var fill:IFill = FilledElement(elem).fill;
if (fill is SolidColor) {
SolidColor(fill).color = color;
}
}
}
}

hope this helps

sorry for the format. Check the source here for an example.