That was one annoying movie. NOTHING happened for the first 45 seconds, and then stuff started going at a snail's pace. A written tutorial with screenshots would have been much better.

Anyway. JSFL is Javascript, not Actionscript. As such, the type declarations should not be present.

Code:
    var jsfl:String = "var doc = fl.getDocumentDOM();var fill = doc.getCustomFill('toolbar');fill.style = 'solid';fill.color = 0x" + colour.toString(16) + ";doc.setCustomFill(fill);";
    MMExecute(jsfl);