Just a quick tip today. It's not so obvious that you can actually drag out colors from the color tray if it gets full or if you simply don't want a color there. Luckily there's a very easy trick to make way for others.
In the color tray there's a "+" sign to add more shades, however, to remove any shade you want simply click and drag it outside of the color tray and voilà! You can make space for other colors :-)