So yeah just ran into this - not a major problem but kind of an inconvenience. The color picker icon the mouse cursor transforms into is just plain white (at least on windows for me, don't know about mac). This gets a little bit in the way when I'm trying to pick a specific region of a mostly - you guess it - white area for using the white balance effect. Just simply an icon that has both black and white parts to it would simply solve this. Have a look at photoshops picker cursor, this one works very well on both light and dark areas.