select some characters before running

var myNewCMYKColor = new CMYKColor;
myNewCMYKColor.magenta = 100;
 
app.activeDocument.selection.fillColor = myNewCMYKColor;

Hi Mark, it might be a bug, at first, in you code selChar is a Character, and in the documentation even though it says "textRange" objects of length 1, there's really no Character Object...but anyhow, selChar does take properties like Contents, behaving like a true textRange Object...but weird it doesn't work when you set the sizes...weird.

then I noticed the textRange Object has a textRanges property, that did it, it holds each character as a textRange.

here's a working sample

var myNewCMYKColor = new CMYKColor;
myNewCMYKColor.magenta = 100;
 
var sel = app.activeDocument.selection;
var characters = sel.textRanges;
var fontsize = sel.characterAttributes.size;
 
for (i=1; i<=characters.length; i++) {
    var character = characters[i];
    var randomFontSize = randomXToY (fontsize-6, fontsize+6);
    character.characterAttributes.size = randomFontSize;
    character.fillColor = myNewCMYKColor;
 
    var randomMagentaColor = randomXToY (0, 100);
    myNewCMYKColor.magenta = randomMagentaColor;
}
 
//function to get random number upto m, by Roshan Bhattarai
function randomXToY(minVal,maxVal,floatVal)
{
  var randVal = minVal+(Math.random()*(maxVal-minVal));
  return typeof floatVal=='undefined'?Math.round(randVal):randVal.toFixed(floatVal);
}

hahaha, that's right, let's have tpa_gru_flo write that as homework

Thats a good spot Carlos… I had seen that but had NOT the time to put it to any tests ( saved me a bother ) There was also a textRange.textSelection that I wasn't sure about… Text ranges and sub ranges are a little weird at times…

ok, you can safely forget all I have said previously

Larry my previous script worked only because I randomly started my selection at the second character, just a coincidence here. I was really iterating the whole textFrame, so ended up rewriting the thing....and at the end it was like Mark's...???...that's weird, how come Marks didn't work?

Mark, I revisited your script and it does not work cos you have a typo , you have newSIze, instead of newSize, changed that and it works beautifully...so, you still need to figure out textRanges and textSelection

here's the new version, it still needs work to make it a real Ransom Note generator

var myNewCMYKColor = new CMYKColor;
myNewCMYKColor.magenta = 100;
 
var sel = app.activeDocument.selection;
 
var fontsize = sel.characterAttributes.size;
 
for (i=0; i<sel.length; i++) {
    var character = sel.characters[i]; //characters[i];
    //alert(character);
    //alert("i= " + i + "\rcharacter= " + character.contents);
    var randomFontSize = randomXToY (fontsize-6, fontsize+6);
    character.characterAttributes.size = randomFontSize;
    character.fillColor = myNewCMYKColor;
 
    var randomMagentaColor = randomXToY (0, 100);
    myNewCMYKColor.magenta = randomMagentaColor;
}
 
//function to get random number upto m, by Roshan Bhattarai
function randomXToY(minVal,maxVal,floatVal)
{
  var randVal = minVal+(Math.random()*(maxVal-minVal));
  return typeof floatVal=='undefined'?Math.round(randVal):randVal.toFixed(floatVal);
}

Looks like I should increase the size of my type in the ESTK I couldn't spot that… Hum a trip to spec savers or a 27" imac… I'll have a think… ( once a muppet always a… )