Okay, I think I have the script you want. Thanks to @r-bin and @pixxxelschubser for the code to change the color and superscript of text items.
#target photoshop
// some code written by r-bin
// other code adapted for actuel requirements by pixxxelschubser
// final code by Chuck Uebele
var doc = app.activeDocument;
var oldPref = app.preferences.rulerUnits;
app.preferences.rulerUnits = Units.PIXELS;
var useSuperscript = false;
var ab, aLayer, aW, aH
var defaultValue = '';
var desktopHead = prompt("Paste your new headline", defaultValue);
var docLayers = doc.layers.length; //getting top layers because artboards are top layers
var color1 = new SolidColor();
with (color1.rgb) { red = 82; green = 176; blue = 52; }
for(var i=0;i<docLayers;i++){
aLayer = doc.layers[i];
ab = artboard_rectangle(aLayer);
aW = ab[2]-ab[0];
aH = ab[3]-ab[1];
if((aW == 1000 && aH == 1000) || (aW == 400 && aH == 500)){//add more sizes here
findTextLayer (aLayer)
}//end if for artboard size
}//end for loop
app.preferences.rulerUnits = oldPref;
function findTextLayer(pLayer){
var layLen = pLayer.layers.length;
for(var j = 0;j<layLen;j++){
var layerRef = pLayer.layers[j];
if(pLayer.layers[j].typename == 'LayerSet'){
findTextLayer (pLayer.layers[j]);
}//end if for finding layerset
else{
if (layerRef.kind === LayerKind.TEXT) {
if(layerRef.textItem.font === "Arial-BoldMT"){//make sure you have correct font name
var layVis = layerRef.visible
doc.activeLayer = layerRef
layerRef.textItem.contents = desktopHead;
var s = activeDocument.activeLayer.textItem.size;
var c = activeDocument.activeLayer.textItem.color;
var f = activeDocument.activeLayer.textItem.font;
var disIdx = layerRef.textItem.contents.indexOf ('discount');
var perIdx = layerRef.textItem.contents.indexOf ('%');
var oneIdx = layerRef.textItem.contents.indexOf ('1');
if(disIdx != -1 && perIdx != -1){
var strLen = perIdx-disIdx+1
setSuperscript (disIdx, strLen, s, color1, f, false)
}
else{alert("a layer doesn't doesn't contain 'discount or %")}
if(oneIdx != -1){
setSuperscript (oneIdx, 1, s, c, f, true)
}
//changeColor ('discount', color1, layerRef)
layerRef.visible = layVis
}//end if for text font
}//end if for layerkind text
}//end else
};//end for loop
};//end function
function artboard_rectangle(layer)
{
try {
var r = new ActionReference();
r.putProperty(stringIDToTypeID("property"), stringIDToTypeID("artboard"));
if (layer) r.putIdentifier(stringIDToTypeID("layer"), layer.id);
else r.putEnumerated(stringIDToTypeID("layer"), stringIDToTypeID("ordinal"), stringIDToTypeID("targetEnum"));
var d = executeActionGet(r).getObjectValue(stringIDToTypeID("artboard")).getObjectValue(stringIDToTypeID("artboardRect"));
var bounds = new Array();
bounds[0] = d.getUnitDoubleValue(stringIDToTypeID("left"));
bounds[1] = d.getUnitDoubleValue(stringIDToTypeID("top"));
bounds[2] = d.getUnitDoubleValue(stringIDToTypeID("right"));
bounds[3] = d.getUnitDoubleValue(stringIDToTypeID("bottom"));
return bounds;
}
catch(e) { alert(e); }
}
function setSuperscript (from, len, size, color, font, superS){
try {
var d = new ActionDescriptor();
var r = new ActionReference();
r.putEnumerated(stringIDToTypeID("textLayer"), stringIDToTypeID("ordinal"), stringIDToTypeID("targetEnum"));
d.putReference(stringIDToTypeID("null"), r);
var d1 = new ActionDescriptor();
var list1 = new ActionList();
var d2 = new ActionDescriptor();
d2.putInteger(stringIDToTypeID("from"), from);
d2.putInteger(stringIDToTypeID("to"), from+len);
var d3 = new ActionDescriptor();
d3.putUnitDouble(stringIDToTypeID("size"), stringIDToTypeID("pointsUnit"), size);
d3.putString(stringIDToTypeID("fontPostScriptName"), font);
if(superS){
d3.putEnumerated(stringIDToTypeID("baseline"), stringIDToTypeID("baseline"), stringIDToTypeID("superScript"));
}
var d4 = new ActionDescriptor();
d4.putDouble(stringIDToTypeID("red"), color.rgb.red);
d4.putDouble(stringIDToTypeID("green"), color.rgb.green);
d4.putDouble(stringIDToTypeID("blue"), color.rgb.blue);
d3.putObject(stringIDToTypeID("color"), stringIDToTypeID("RGBColor"), d4);
d2.putObject(stringIDToTypeID("textStyle"), stringIDToTypeID("textStyle"), d3);
list1.putObject(stringIDToTypeID("textStyleRange"), d2);
d1.putList(stringIDToTypeID("textStyleRange"), list1);
d.putObject(stringIDToTypeID("to"), stringIDToTypeID("textLayer"), d1);
executeAction(stringIDToTypeID("set"), d, DialogModes.NO);
}
catch (e) { throw(e); }
}