I have various buttons then when pressed cause a certain area of the page to be highlighted (to draw attention to it).
When I hit the buttons after each other quite quickly it used to crash (fixed by using a single events queue!) but now I see that the highlight colour stays around.
It appears (just by observation) as if the "overlayed" highlight stores the colour for the background (the one to restore when it's complete) as the currently processing highlight colour and restores that colour, incorrectly, when it finishes.
