The new 3.0 App includes a dedicated whites screen to help you find the perfect shade of white for you. From the Dashboard, tap on a group that you would like to adjust and drill down to group level settings. Then tap or swipe the top navigation to the right until you reach the whites like below.
Once you tap a white setting, you can adjust the brightness of your white by using the arrows to the left and right.
Much like the Color screen, you can easily create a favorite from your selected setting or save it as your master default at the bottom of the screen.