The app also adds support for the Pogo Connect stylus, an $80 drawing tool that uses Bluetooth 4.0 to determine how hard an artist is drawing and Paper adjusts accordingly.
The Verge has more on how the new color mixer works:
Paper now includes a circular color mixer that lets you tap to pick a color (using RGB sliders, if you'd like), then swipe in a circle clockwise to mix colors and counter-clockwise to unmix. A long press lets you save the color you've made to one of the many black color slots the app now provides. Color is a $1.99 in-app purchase, like many of the app's add-on brushes. If you don't choose to buy it, you still have access to the palette of colors that shipped with the free app.
Paper for iPad is a free download from the App Store, with additional drawing brushes and the color picker available as in-app purchases. [Direct Link]