removing swatch colour from character style

Hi,

I'm doing a find/change via script to remove the fill colour from a character style.

So far I've got it to replace the current colour with None, using this:

   app.changeGrepPreferences.fillColor = myDocument.colors.item("None");

But what I really need is to replace it with the question mark symbol, like below, so it can inherit another colour I've applied via a grep style.

Doing this manually in Indesign I would Control+click the swatch.

I've spent the last couple of days looking for the magic bit of code I'm missing with no luck, hopefully you guys can help.

Cheers,

John