Set focus back to score

I have a guitar tab plugin which has an option to set the note colour for left hand fingering. It works but after clicking a colour button the focus stays on the docked plugin window. How do I set the focus back to the score note so that I can continue to arrow left and right through the score?

The colour setting is done like this:

function setFingerColour(fing)
{
    var note = find_note();
    if (!note) return false;
    note.color = fingrgb[fing];
}