should save a txt on the desktop which includes used swatches:
#target indesign
app.doScript(mySwatches, ScriptLanguage.JAVASCRIPT, undefined, UndoModes.ENTIRE_SCRIPT)
function mySwatches()
{
//delete unused swatches
try{
app.menuActions.itemByID(16395).invoke();
app.menuActions.itemByID(16391).invoke();
}catch (e){}
var cS = app.activeDocument.swatches.everyItem().name.join('\n');
with(File('~/Desktop/mySwatches.txt'))
{
open('W');
write(cS);
close()
}
}
//undo the script, eg deleting swatches
app.activeDocument.undo()