Sets the gray scale color of each text item in a group of a given name to a smooth gradient

text_gradient.js

var layerSetText = app.activeDocument.layerSets.getByName("GROUPNAME")

for (var i=0; i<layerSetText.artLayers.length; i++) {
	var col = new SolidColor();
	var grayCol = new GrayColor();
	grayCol.gray = i*100.0/(layerSetText.artLayers.length-1);
	col.gray = grayCol;

	layerSetText.artLayers[i].textItem.color = col;
}